Induction heating device, induction heating equipment, induction heating method, and heat treatment method

ABSTRACT

An induction heating device is provided. The induction heating device comprises a plurality of induction heating devices disposed at intervals along the circumference of a ring-shaped workpiece, a setting unit for setting induction heating conditions, and a switching control unit. Each of the plurality of induction heating devices comprises heating coils disposed facing areas to be heated of the workpiece, a plurality of transformers connected to the heating coils in parallel, a plurality of matching units connected to any one of the plurality of transformers, an inverter unit having a rectifier unit and an inverter unit, an inverter control unit having a rectification control unit, and a group of switches.

This application is a divisional of U.S. application Ser. No. 16/037,761filed on Jul. 17, 2018, which is a divisional of U.S. application Ser.No. 14/110,410 filed on Jan. 13, 2014, which is a continuation ofInternational Application No. PCT/JP2012/059607 filed on Apr. 6, 2012.

TECHNICAL FIELD

The present invention relates to an induction heating device andinduction heating equipment for heating a workpiece by inductionheating, an induction heating method, and a heat treatment method.

BACKGROUND ART

Induction heating is performed for a workpiece where areas to be heatedare established so as to extend in one direction. Heat treatmentequipment such as follows has been proposed to heat a large workpiece ina shape of a ring, for example: heating coils are disposed so as to facea portion of areas to be heated extending in one direction on aworkpiece, and by rotating the workpiece, for example, the entire lengthof the areas to be heated of this workpiece is heated.

The following Patent Reference 1 discloses high-frequency heat treatmentequipment capable of heating a ring-shaped workpiece such as a largebearing ring. With this technique, a plurality of horseshoe-shapedheating coils are disposed at places along the circumferential directionof the ring-shaped workpiece, the induction heating is performed by theplurality of heating coils while the ring-shaped workpiece is beingrotated, and after the heating, a cooling liquid is discharged from eachof the horseshoe-shaped heating coils to rapidly cool the workpiece forheat treatment.

The following Patent Reference 2 discloses a device for performinginduction heat treatment of the entire body of a ring-shaped piece. Withthis technique, positioning of the outside surface and inside surface ofthe ring-shaped piece is performed using a positioning roller, heatingcoils are disposed partially on the inner periphery, outer periphery,side face, etc. of the ring-shaped piece, the induction heating isperformed while the ring-shaped piece is being rotated, and then rapidcooling is performed as heat treatment.

An induction heating device for applying electric power to heating coilsas described below is generally used. Namely, such an induction heatingdevice includes: an inverter for converting commercial power into directcurrent once and then converting it into alternating current having apredetermined frequency; a transformer including a primary windingconnected to the inverter and a secondary winding; matching unitsconnected in parallel to the primary winding of the transformer; and aheating coil connected to the secondary winding of the transformer. Theheating coil and a workpiece are inductively coupled to ensure matchingbetween the inverter and the heating coil.

The induction heating device disclosed in Patent Reference 3 isconfigured by connecting a capacitor and a matching transformer to aself-controlled thyristor inverter as a power supply, connecting a groupof taps for selecting proper voltage and proper frequency at the time ofincreasing-temperature heating of an object to be heated, connectinganother group of taps for selecting proper voltage and proper frequencyat the time of constant-temperature heating of the object to be heated,and connecting each group of taps to a heating coil via a selectorswitch.

PRIOR ART REFERENCE Patent Reference

Patent Reference 1: JP 2005-325409 A

Patent Reference 2: JP 2009-287074 A

Patent Reference 3: JP 1988-42830 B

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, with the heating devices adopting prior art induction heating,it was not easy to increase the temperature of areas to be heated to adesired level when a large workpiece was subjected to quenching. In thecase of a large workpiece, disposing heating coils so that they face theentire areas to be heated increases costs significantly, and it istherefore infeasible. Therefore, there was no other choice but to useheating coils facing a portion of the areas to be heated. In this case,heating must be performed for a long time because the amount of steelwith respect to the areas to be heated is large. In addition, thedeformation amount due to thermal expansion of the workpiece increaseswith time, and consequently, optimum heating conditions cannot bemaintained.

In particular, when areas of the workpiece to be heated extend in onedirection, and the deformation amount that appears on one edge of theareas to be heated due to thermal expansion is different from that onthe other, the workpiece deforms non-uniformly. Consequently, with largeworkpieces, it was difficult to increase the temperature of the entireareas to be heated uniformly to a predetermined high temperature usingheating coils.

A first object of the present invention is to provide an inductionheating device and an induction heating method that ensure facilitatedand approximately uniform heating of the entire areas to be heated of aworkpiece even if the workpiece is large, and also ensure uniformheating even if non-uniform deformation should occur during heating.

To subject a large workpiece having a radius of 1 m or larger, 3 m forexample, to induction heating, the following method is adopted to heatthe entire areas to be heated of the workpiece: a part of the areas tobe heated of a workpiece is locally subjected to induction heating whilethe workpiece itself is rotated. In this case, since the temperature ofthe areas to be heated does not increase in several seconds, the heatingtime of several minutes is required.

However, if heating is performed for a long time, the output impedanceviewed from the inverter changes with time, making it difficult forelectric power to be applied from the inverter to the heating coils viamatching units and transformers, and thus it becomes impossible to heatthe workpiece to a predetermined temperature.

A second object of the present invention is to provide a heating device,heating equipment, and a heating method capable of increasing thetemperature of a workpiece to a predetermined temperature by inductionheating even if relatively long time is needed.

Conventionally, when performing heat treatment of a ring-shaped area tobe heated, the entire surface of the workpiece or the entire area to beheated of the workpiece is heated collectively, and then the entire areais cooled rapidly as heat treatment. With such a heat treatment method,when a workpiece having a plurality of ring-shaped areas to be heated issubjected to heat treatment, for example, a large number of heatingcoils are required depending on the shape and the size of the workpiecebecause the plurality of areas to be heated are heated and cooledcollectively. In addition, the shape and the structure of the heatingcoils and a work supporting structure, hence the device structure,become complicated.

Furthermore, with the structure where the plurality of areas to beheated are heated and cooled collectively, the areas to be heated usingheating coils are large, and consequently, large power is required. Inthe case of a large workpiece, unless sufficient amount of power is fed,the temperature of the areas to be heated cannot be increased to adesired level. To feed sufficient amount of power, bulk powerappropriate to the size of the workpiece is necessary, and thus the sizeof power supply facilities increases.

Meanwhile, if each of the areas to be heated of the workpiece having aplurality of ring-shaped areas to be heated is heated one by one, as aresult of subjecting some areas to be heated to heat treatment, astructure different from that of other areas is formed on the workpieceendlessly. Consequently deformation tends to occur, causing heattreatment defects, such as hardening cracks and deformation, to occurafter heat treatment. In the case of large workpieces, in particular, itwas found that once such a transformation structure is generated in alocal ring-shaped area, deformation and stress also increase with theincrease of the size of the workpiece, thus causing heat treatmentdefects to occur easily.

A third object of the present invention is therefore to provide a heattreatment method that can be used to heat-treating a plurality ofring-shaped areas to be heated on a workpiece with a simple structure. Afourth object of the present invention is to provide a heat treatmentmethod capable of preventing heat treatment defects from occurring whenring-shaped areas to be heated are set on a workpiece and each area issubjected to heat treatment.

Means for Solving Problem

In order to achieve the first object, the present invention provides aheating device for induction-heating a workpiece, on which areas to beheated are established extending in one direction, and when the areas tobe heated are induction-heated, the side of one edge and the side of theother edge of the areas to be heated exhibit different deformationamounts, comprising: heating coils facing a portion of the areas to beheated; and a relative transfer means for transferring the workpiece andthe heating coils along the direction in a relative manner, wherein theheating coils are disposed so as to correspond to the areas to be heatedduring heating period.

The inducting heating device to achieve the first object preferablyfurther comprises: a displacing means for changing the orientation ofthe heating coils around a shaft along the direction in order that thesurface of the heating coils facing the area to be heated follows thearea to be heated during the heating period.

In the induction heating device to achieve the first object, thedisplacing means preferably further comprises: a posture control unitfor controlling the operation of the displacing means in the displacingmeans so as to minimize or eliminating the difference in the anglebetween the surface of the heating coils facing the area to be heatedand the area to be heated during the heating period, wherein the posturecontrol unit includes: a setting input unit for inputting heatingconditions of the workpiece; an arithmetic processing unit forcalculating the relative angle between the surface of each heating coilsfacing the areas to be heated and the areas to be heated in set heatingstate of the areas to be heated; a heating state evaluating unit forevaluating that the heating state of the areas to be heated has reachedthe set heating state; and a driving control unit for driving thedisplacing means when the set heating state has been reached.

In the induction heating device to achieve the first object, thearithmetic processing unit calculates the relative angle in the setheating state by predetermined simulation processing based on theheating conditions, thereby calculating the angle between the surface ofthe heating coils facing the areas to be heated and the areas to beheated.

The induction heating device to achieve the first object, furthercomprises: a position detecting means for detecting surface positions ofthe workpiece other than the areas to be heated during the heatingperiod; and a displacing means for displacing the relative positionbetween the workpiece and the heating coils based on the detectionresult of the position detecting means, wherein the displacing meanscorrects measurement positions obtained by the detection result duringthe heating period based at least on the shape of the workpiece, anddisplaces the relative position between the workpiece and the heatingcoils so as to correspond to the corrected positions obtained bycorrection.

In the inducting heating device to achieve the first object, themeasurement positions are measured as displacements from a referenceposition, the corrected positions are corrected displacements obtainedby correcting the measured displacements, and it is preferable that thedisplacing means changes the relative position of the workpiece and theheating coils so that it corresponds to the corrected displacements.

In the induction heating device to achieve the first object, thedisplacing means is preferably provided with a posture control unit forcontrolling its operation of the displacing means in the displacingmeans, wherein the posture control unit corrects the measurementpositions using a correction coefficient corresponding at least to theshape of the workpiece, thereby obtaining the corrected positions, andat the same time, controls the operation of the displacing means so asto correspond to the corrected positions.

In the induction heating device to achieve the first object, the posturecontrol unit preferably comprises: a setting input unit for inputtingthe heating conditions of the workpiece; a storage unit for storing thecorrection coefficient in the set heating state of the areas to beheated; a heating state evaluating unit for evaluating that the heatingstate of the areas to be heated has reached the set heating state; anarithmetic processing unit for calculating the corrected positions fromthe measurement positions and the correction coefficient; and a drivingcontrol unit for driving the displacing means so as to correspond to thecorrected positions.

In the induction heating device to achieve the first object, thearithmetic processing unit preferably calculates the correctioncoefficient in the set heating state by the predetermined simulationprocessing based on the heating conditions, and the storing unitpreferably stores the correction coefficient obtained by the arithmeticprocessing unit by allowing it to correspond to the set heating state.

The induction heating method to achieve the first object, forinduction-heating a workpiece where areas to be heated are establishedextending in one direction, the deformation amount that appears on oneedge of the areas to be heated when the areas to be heated areinduction-heated being different from that on the other, it comprises: aheating process for allowing heating coils to face a portion of theareas to be heated and for heating the workpiece using the heating coilswhile the workpiece and the heating coils are made to move along thedirection in a relative manner, wherein the heating coils are disposedso as to follow the areas to be heated during heating period.

In the induction heating method to achieve the first object, it ispreferable that the surface of the heating coils facing the areas to beheated is made to follow the areas to be heated during the heatingperiod.

In the induction heating method to achieve the first object, it ispreferable that further detecting surface positions of the workpieceother than the areas to be heated during the heating period; correctingmeasurement positions obtained by detection result based at least on theshape of the workpiece; and changing relative positions between theworkpiece and the heating coils so as to correspond to correctedpositions obtained by the correction.

Another induction heating device to achieve the first object is aheating device for induction-heating a workpiece, on which areas to beheated are established extending in one direction. The device comprises:a plurality of heating coils facing a portion of the areas to be heated;a relative transfer means for transferring the workpiece and theplurality of heating coils along the direction in a relative manner; anda displacing means for displacing the positions of the heating coilsindividually in the width direction of the areas to be heated, whereinthe displacing means displaces each of the heating coils, thereby makingadjustment so that the area where the plurality of heating coils and theareas to be heated face each other changes in the width direction of theareas to be heated, and heating the areas to be heated by the pluralityof heating coils.

In yet another induction heating device to achieve the first object,wherein the deformation amount that appears on one edge of the areas tobe heated of the workpiece when the areas to be heated areinduction-heated is different from that on the other, further itcomprises: a posture control unit for controlling the operation of thedisplacing means in the displacing means, wherein the posture controlunit displaces the position of each of the heating coils correspondingto a gap between the areas to be heated and each of the heating coilsduring heating period.

Yet another induction heating device to achieve the first object ispreferably equipped with a power adjusting means for individuallyadjusting high-frequency power to be supplied to the plurality ofheating coils, and it is preferable that the displacing means adjuststhe position of each of the heating coils, and the power adjusting meansvaries high-frequency power to be fed to each of the heating coils,thereby allowing the plurality of heating coils to heat the areas to beheated.

In yet another inducting heating device to achieve the first object, theposture control unit preferably comprises: a setting input unit forinputting heating conditions of the workpiece; an arithmetic processingunit for determining the disposition of the plurality of heating coilscorresponding to the gap between the areas to be heated and theplurality of heating coils in assumed heating conditions of the areas tobe heated; a heating state evaluating unit for evaluating that theheating state of the areas to be heated has reached the assumed heatingstate; and a driving control unit for driving the displacing means basedon the disposition of the plurality of heating coils when the assumedheating state has been reached.

In yet another induction heating device to achieve the first object, thearithmetic processing unit may determine the disposition of theplurality of heating coils by calculating the gap in the assumed heatingstate by the predetermined simulation processing based on the heatingconditions.

Another induction heating method to achieve the first object is aheating method for induction-heating a workpiece, on which areas to beheated are established, extending in one direction. The method comprisesthe step of: heating for allowing heating coils to face a portion of theareas to be heated, thereby heating the workpiece by the heating coilswhile the workpiece and the heating coils are made to move along thedirection in a relative manner; and displacing the plurality of heatingcoils individually in the width direction of the areas to be heatedduring heating period, thereby making adjustment so that the area wherethe plurality of heating coils and the areas to be heated face eachother changes in the width direction of the areas to be heated.

In order to achieve the second object, the present invention provides aninduction heating device comprising: a plurality of transformersconnected to heating coils in parallel; a plurality of matching unitsconnected to any one of the plurality of transformers; an inverter unithaving a rectifier unit for converting commercial power voltage to DCvoltage, and an inverter unit for converting the DC voltage obtained bythe rectifier unit into a voltage having a specified frequency; aninverter control unit having a rectification control unit forcontrolling the rectifier unit and a plurality inversion control unitfor controlling the inverter unit, thereby obtaining voltagesrespectively having specified frequencies; a group of switches forconnecting the heating coils to any one of the plurality oftransformers, connecting any one of the plurality of transformers to anyone of the plurality of matching units, connecting any one of theplurality of matching units to the inverter, and connecting any one ofthe plurality of inverter control units to the inverter unit; a settingunit for setting the frequency setting information on the voltage outputfrom the inverter and selection information of matching circuits, namelycombinations of selections of the plurality of matching units and theplurality of transformers, for each of the divisions obtained bydividing induction heating time into divisions, as induction heatingconditions; and a switching control unit for selecting any one of theplurality of inversion control units to control the inverter unit andoutputting a voltage having a specified frequency, connecting a matchingunit to the inverter using the group of switches, connecting thematching unit to a transformer; and connecting the transformer to theheating coils, for each of the divisions in accordance with theinduction heating conditions set by the setting unit.

In the induction heating device to achieve the second object, theinverter is preferably equipped with an impedance measuring unit formeasuring output impedance in the inverter, and it is preferable that inan event the measurement result input from the impedance measurementunit exceeds the allowable range, the switching control unit selects anyone of the plurality of inversion control units, and changes thefrequency of the voltage output from the inverter and switches the groupof switches, thereby ensuring impedance matching, by referring toconditions associated with the next division, of the induction heatingconditions set in the setting unit.

Induction heating equipment to achieve the second object comprises: aplurality of induction heating devices disposed at intervals along thecircumference of a ring-shaped workpiece; a setting unit for settinginduction heating conditions; and a switching control unit, wherein eachof the plurality of induction heating devices comprises: heating coilsdisposed facing areas to be heated of the workpiece; a plurality oftransformers connected to the heating coils in parallel; a plurality ofmatching units connected to any one of the plurality of transformers; aninverter unit having a rectifier unit for converting commercial powervoltage to DC voltage and an inverter unit for converting the DC voltageobtained by the rectifier unit to a voltage having a specifiedfrequency; an inverter control unit having a rectification control unitfor controlling the rectifier unit and a plurality of inversion controlunits for controlling the inverter unit, thereby obtaining voltageshaving specified frequencies; and a group of switches for connecting theheating coils to any one of the plurality of transformers, connectingany one of the plurality of transformers to any one of the plurality ofmatching units, connecting any one of the plurality of matching units tothe inverter, and connecting any one of the plurality of inversioncontrol units to the inverter unit, wherein the setting unit setsfrequency setting information on the voltage output from the inverterand the selection information of matching circuits, namely combinationsof selections of the plurality of matching units and the plurality oftransformers, for each of the induction heating devices, or for each ofthe divisions obtained by dividing induction heating time into aplurality of divisions, as induction heating conditions, and theswitching control unit selects any one of the plurality of inversioncontrol units, and controls the inverter unit, thereby outputting avoltage having a specified frequency, connects a matching unit to theinverter, connects the matching unit to a transformer, and connects thetransformer to the heating coils by using the group of switches, foreach of the induction heating devices and by the division, in accordancewith the induction heating conditions set by the setting unit.

In order to achieve the second object, the present invention provides aninduction heating method, comprising the step of: varying the frequencyof induction current to be fed to the workpiece depending on the heatingtemperature or heating time of the workpiece when a workpiece isinduction-heated while being moved; and changing the combinations ofmatching units and transformers in accordance with the change infrequency.

In order to achieve the second object, the present invention providesanother induction heating method, comprising the step of: disposing aplurality of heating coils along a workpiece; varying the frequency ofthe induction current fed to the workpiece depending on the heatingtemperature or heating time of the workpiece when induction heating isperformed by the plurality of heating coils while the workpiece ismoved; and changing combinations of matching units and transformersdepending on the change in frequency.

A heat treatment method in order to achieve the third and the fourthobjects, the present invention provides a heat treatment method forproviding a plurality of ring-shaped areas to be heated along aring-shaped workpiece and performing heat treatment sequentially foreach of the areas to be heated, comprising: a first heating process forheating a first area to be heated; a first cooling process for rapidlycooling the heated first area to be heated; a tempering process forheating and cooling the first area to be heated after the first coolingprocess is completed; and a second heating process for heating thesecond area to be heated after the tempering process is completed.

In the heat treatment method to achieve the third and the fourth object,it is preferable that the deformation amount that appears on one edge ofthe areas to be heated when the areas to be heated are heated isdifferent from that on the other.

In the first heating process and the tempering process of the heattreatment method to achieve the third and the fourth objects, the firstarea to be heated is preferably induction-heated by using the sameheating coils in the first heating process and the tempering process.

In the first heating process and the second heating process of the heattreatment method to achieve the third and the fourth objects, the firstarea to be heated and the second area to be heated are preferablyinduction-heated by using the same heating coils in the first heatingprocess and the second heating process.

In the heat treatment method to achieve the third and the fourthobjects, the first area to be heated and the second area to be heatedpreferably have plane-symmetrical shape, and the workpiece is preferablyinverted after the tempering process.

Effect of Invention

According to the induction heating device and the inducting heatingmethod to achieve the first object of the present invention, since theheating coils are disposed so as to correspond to the areas to be heatedduring heating period, or disposition/distribution of the plurality ofheating coils in the width direction is adjusted, the temperature of theentire area to be heated can be increased uniformly to a designatedtemperature, even if the deformation amount that appears on one edge ofthe area to be heated when the workpiece is induction-heated isdifferent from that on the other.

According to the induction heating device, induction heating equipment,and inducting heating method to achieve the second object of the presentinvention, by varying the frequency output from the inverter dependingon the heating temperature or heating time of the workpiece, and at thesame time by changing the combinations of the matching units and thetransformers, impedance can be adjusted, and thus sufficient electricpower can be supplied to the workpiece and the temperature can beincreased to a desired level. In particular, impedance matching isensured by increasing the temperature of the areas to be heated of theworkpiece to suite the magnetic permeability.

According to the heat treatment method to achieve the third object ofthe present invention, since ring-shaped areas to be heated matching theshape of the workpiece are provided at a plurality of positions of thering-shaped workpiece and the plurality of areas to be treated aresequentially subjected to heat treatment, heating can be performed usingthe heating unit having a configuration corresponding to the shape ofthe areas to be heated, regardless of the size and the shape of theworkpiece. Consequently, the area to be heated can be heated using asimple heating unit that does not depend on the size or the shape of theworkpiece, and thus a heat treatment method ensuring heat treatmentusing simple-structure heat treatment equipment can be provided.Furthermore, according to this heat treatment method, when thering-shaped areas to be heated matching the shape of the workpieceprovided locally at the plurality of positions along the ring-shapedworkpiece are sequentially subjected to heat treatment, the first areato be heated is subjected to heat treatment in the first heating processand in the first cooling process, the first area to be heated is heatedand cooled in the subsequent tempering process, and then the second areato be heated is heated. Consequently, occurrence of heat treatmentdefects such as deformation and hardening cracks can be decreased orprevented during a period until the second area to be heated is heatedor while heating is performed.

BRIEF DESCRIPTION OF DRAWINGS

In the drawings:

FIG. 1 is a partial cross-sectional view of a workpiece to be heated ofthe present invention;

FIG. 2 is a plan view of heat treatment equipment according to theembodiment of the present invention;

FIG. 3 is a side view of the heat treatment equipment according to theembodiment of the present invention, not showing a heating unit providedon the front side;

FIG. 4 is a side view of the heat treatment equipment according to theembodiment of the present invention, with a part of it shown incross-sectional view so that a state where a jig of the heat treatmentequipment is connected to a transfer loader is shown;

FIG. 5 is a chart showing the main menu screen of the operation unit ofthe heat treatment equipment according to the embodiment of the presentinvention;

FIG. 6 is a view showing a mobile terminal of the operation unit of theheat treatment equipment according to the embodiment of the presentinvention;

FIG. 7 is a schematic plan view showing a heating section of the heattreatment equipment according to the embodiment of the presentinvention;

FIG. 8 (a) is a side view of a heating unit and a displacing means ofthe heating section according to the embodiment, (b) is their rear view,and (c) is their partial plan view;

FIG. 9 is a partial side view of a position detecting unit of theheating section according to the embodiment of the present invention;

FIG. 10 is a partial cross-sectional view of a cooling section accordingto the embodiment of the present invention;

FIG. 11 is a circuit diagram of power feeding equipment of the heattreatment equipment according to the embodiment of the presentinvention;

FIG. 12 is a chart schematically showing the step data setting screenthat appears on the input/output screen of the operation unit of powerfeeding equipment;

FIG. 13 is a chart schematically showing the circuit setting conditionsetting screen that appears following the step data setting screen shownin FIG. 12;

FIG. 14 is a chart schematically showing the output characteristics ofthe inverter in a circuit configuration different from FIG. 11, obtainedwhen induction heating was performed in relatively short time with thefrequency of the output from the inverter unchanged during heating;

FIG. 15 is a schematic cross-sectional view for describing non-uniformdeformation of the workpiece, exaggeratingly showing the deformation;

FIG. 16 is a block diagram showing a posture control unit according tothe embodiment of the present invention;

FIG. 17 is a flow chart showing the heating process according to theembodiment of the present invention;

FIG. 18 is a schematic cross-sectional diagram showing the heated stateof the workpiece in the heat treatment equipment according to theembodiment of the present invention, exaggeratingly displaying thedeformation;

FIG. 19 is a development view showing the disposition of coils in theheat treatment equipment according to the embodiment of the presentinvention;

FIG. 20 (a) is a front view of a heating coil of the heat treatmentequipment according to the embodiment, (b) is a partial front viewshowing the shape of the part of the heating coil facing the workpiecein a variation of the heating coil, and (c) is a partial front viewshowing the shape of the part of the heating coil facing the workpiecein another variation;

FIG. 21 is a flow chart showing the process of subjecting the first areato be heated and the second area to be heated to heat treatmentaccording to the embodiment of the present invention;

FIG. 22 (a) to (d) are charts describing heat treatment procedures ofthe first area to be heated according to the embodiment of the presentinvention; and

FIG. 23 (a) to (d) are charts describing heat treatment procedures ofthe second area to be heated according to the embodiment of the presentinvention.

MODES FOR CARRYING OUT THE INVENTION

The embodiment of the present invention will hereinafter be explained indetail by referring to the drawings.

This embodiment will be explained by referring to an example where alarge ring-shaped object to be heated is heated and cooled as heattreatment.

In this case, heat treatment is defined as treatment whereby a workpieceW is subjected to heating and cooling in combination under variousconditions, thereby changing the structure, hence the properties, of theworkpiece such as hardness and toughness. Heat treatment includesquenching, for example.

First Embodiment [Workpiece]

A workpiece, namely an object to be heated in the present invention,will be explained first.

The workpiece to be heated is a heat-treatable material such as steel,and either the one whose surface only can be heated or the one whoseinner part also can be heated may be used as the workpiece. On a part ofthe surface of the workpiece, areas to be heated are established,extending in one direction in roughly a constant shape. In particular,application to a workpiece wherein the entire length of the areas to beheated is longer than their width, namely a distance between the bothedges of the areas to be heated, is favorable. In the case of aworkpiece having edges, one direction is defined as a direction along astraight line, undulating line, curved line, etc. extending between theboth edges. In the case of a ring-shaped workpiece, it is the directionalong the shape of the ring.

The shape of the workpiece is arbitrarily selectable, but the presentinvention is favorably applicable to a workpiece wherein the deformationamount, that appears due to thermal expansion on one edge in the widthdirection of the areas to be heated when the areas to be heated areinduction-heated, is different from that on the other. For example, ifthe shape of one edge and that of the other edge of the areas to beheated are significantly different from each other viewed as a crosssection perpendicular to the areas to be heated, the deformation amountthat appears on both edges of the areas to be heated due to thermalexpansion caused by induction heating becomes different.

As shown in FIG. 1, workpiece W in this embodiment is in a shape of aring, and on its surface, areas to be heated H1, H2 are provided locallyat two or more positions. Each of the areas to be heated H1, H2 isprovided in a shape of a ring along the ring shape of the workpiece W.

The workpiece W is in a shape of a ring, and in its cross-sectionalview, has a base W1 and a protrusion W2 protruding inward from the baseW1. The protrusion W2 has inclined surfaces W3 inclining inward inreverse directions. On one of the inclined surfaces W3, a first area tobe heated H1 is provided, and on the other inclined surface W3, a secondarea to be heated H2 is provided endlessly along the shape of the ringrespectively. The first and the second areas to be heated H1, H2 may beareas whose surface only is to be heated, or those whose internalregions also can be heated, but in this embodiment, the surface only isthe area to be heated.

This workpiece W is an example of an outer ring constituting a largering-shaped rotating ring or an outer ring constituting a large bearingetc. having a diameter of 1 m or larger, 3 m or larger in this case.

In this workpiece W, the first and the second areas to be heated H1, H2extend almost in parallel to each other in roughly a constant shape. Thefirst area to be heated H1 and the second area to be heated H2 areplane-symmetrical: by inverting one edge and the other edge of theworkpiece W, the first area to be heated H1 and the second area to beheated H2 are disposed in the same positions.

The workpiece is in a shape allowing the of deformation amount thatappears due to thermal expansion on one edge in the width direction ofthe areas to be heated H1, H2 to differ from that on the other when oneor both of the areas to be heated H1, H2 is/are subjected to inductionheating. The reason for this is as follows: the deformation amount dueto thermal expansion that appears when both edges of the areas to beheated H1, H2 are subjected to induction heating differ because theshape of one edge and that of the other edge of the areas to be heatedH1, H2 are significantly different from each other in cross-sectionalview perpendicular to the areas to be heated H1, H2.

[Heat Treatment Equipment]

Heat treatment equipment using an induction heating device in thisembodiment will be explained below. In this embodiment, inductionheating equipment having an induction heating device, a setting unit forsetting induction heating conditions, and a switching unit is alsoreferred to as an induction heating device to facilitate understanding.

As shown in FIG. 2 to FIG. 4, heat treatment equipment 10 includes: ajig 100 for supporting the workpiece W; a bring in/out section 300 forbringing in/out the workpiece W; a transfer mechanism 200 for hoistingand transferring the jig 100; a heating section 400 for heating theworkpiece W placed on the jig 100 while rotating it; a cooling section500 installed at a place lower than the heating section 400; a partsreplacement section 600 installed on the opposite side of the bringin/out section 300; and electrical facilities for driving each section.

As shown in FIG. 4, the jig 100 includes: a workpiece supporting member110 on which a workpiece W is placed; and a central structure 130installed at the center of the workpiece supporting member 110. Theworkpiece supporting member 110 is equipped with rotating rollers 112arranged in a radial fashion on the side of the tip of a plurality ofradial racks 111 extending in radial direction as relative transfermeans. The rotating rollers 112 can be rotationally driven by a drivingforce input to the central structure 130. The workpiece W can be movedalong the shape of a ring by rotating each of the rotating rollers 112.

As shown in FIG. 2 and FIG. 3, the bring in/out section 300 isstructured to place the workpiece W on the workpiece supporting member110 of the jig 100 at bring in/out position P1, transfer it to asuspending position P2, and place the jig 110 accurately at thesuspending position P2.

As shown in FIG. 2 and FIG. 3, the transfer mechanism 200 has transferrails 210 installed above each sections and a transfer loader unit 220that travels along the transfer rails 210. As shown in FIG. 4, thetransfer loader 220 can be connected to the central structure 130 of thejig 100, and is structured to suspend and transfer the jig 100 inconnected state. The transfer loader 220 is provided with a rotationdriving means 246. By connecting the transfer loader 220 to the centralstructure 130 of the jig 100, each of the rotating rollers 112 of thejig 100 is driven to rotate by the rotation driving means 246.

As shown in FIG. 2 and FIG. 3, the heating section 400 has a structure,to which the present invention is applied, wherein the workpiece Wplaced on the jig 100 is uniformly heated while being made to rotate ina state where the jig 100 is placed at a predetermined position. Detailswill be described later.

As shown in FIG. 3, the cooling section 500 is installed below theheating section 400, and supplies cooling liquid from the cooling jacket520, thereby cooling the workpiece W while rotating it, in a state wherethe jig 100 is lowered.

As shown in FIG. 2 and FIG. 3, the parts replacement section 600 is usedto replace the parts of each section by allowing parts replacement jig620 to support and transfer the parts of the heating section 400 and thecooling section 500.

The electrical facilities are structured to feed power to all thesections, and equipped with an operating unit 710 for controlling andoperating each operating unit of all the sections. The operating unit710 is equipped with a touch panel as shown in FIG. 5, on whichinformation for each section can be entered and operation can bemonitored. On the main menu of the operating unit 710 as shown in FIG.5, monitor, model selection, heating condition selection, measurementdata, and parameter screens of each section can be selected to enter ordisplay desired items.

This operating unit 710 includes a mobile terminal 701 as shown in FIG.6 that can be carried around easily by an operator. With this mobileterminal 701, monitor, model selection, heating condition setting,measurement data, and parameter screens of each section can be selectedto enter or display desired items so that the same operation as theoperating unit 710 can be performed. This mobile terminal 701 is used byconnecting terminals, which are provided at more than one positionsurrounding the heat treatment device 10, with use of wire i.e. a cable702.

In this case, since connections are provided at more than one positionsof the heat treatment equipment 10, the operator can perform variousentry or other operations at various places of the heat treatmentequipment 10 without traveling to the operation panel of the operatingunit 710. Furthermore, since it is connected by wire using the cable702, communication failures can be prevented and thus proper operationsare ensured even with devices for performing heat treatment usinghigh-frequency waves.

[Entire Configuration of the Heating Section]

As shown in FIG. 7, the heating section 400 includes: jig supportingmechanisms 410 for supporting the radial racks 111 of the jig 100 fromunder and controlling their transfer in the circumferential direction;and a plurality of heating units 450 for heating the workpiece W placedon the jig 100. The plurality of jig supporting mechanisms 410 andheating units 450 are provided circumferentially around the center ofrotation C of the workpiece W, namely the center of the jig 100. In thiscase, workpiece W heating positions P3 are provided between the radialracks 111 of the jig 100 placed adjacent to each other, and each heatingunit 450 is disposed so as to correspond to the heating position P3.

[Heating Unit]

As shown in FIG. 7 and FIG. 8, each heating unit 450 has a positiondetecting means 480 for detecting surface positions on the workpiece W,and a heating coil 451 placed facing the areas to be heated H1, H2 ofthe workpiece W placed on the jig 100 at each heating position P3.Furthermore, each heating unit 450 includes: power feeding equipment700, which is a part of the electrical facilities, for controlling eachpart of the heating unit 450 and feeding high-frequency power to theheating coil 451; a supporting box 452 for connecting and supporting theheating coil 451; a displacing means 460; a posture control unit 490; apower adjusting means 491; and an auxiliary cooling unit 440. Thedisplacing means 460 displaces the relative position, and changes therelative angle, of the heating coil 451 with respect to the workpiece Wby displacing and changing the orientation of the supporting box 452based on the result of detection of the position detecting means 480.The posture control unit 490 controls the operation of the displacingmeans 460 to adjust the relative position and relative angle of theworkpiece W and the heating coil 451. The power adjusting means 491,which is a part of the power feeding equipment 700, adjusts thehigh-frequency power fed to the heating coils 451. The auxiliary coolingunit 440 sprays cooling liquid, while one of the areas to be heated H1,H2 is being heated, to the other portion, the other area to be heatedH1, H2, in particular, to cool the portion.

[Position Detecting Means]

The position detecting means 480 detect the position of the surface ofthe workpiece during heating. As shown in FIG. 7, they are disposedupstream of each heating position P3. In this embodiment, they aredisposed between every two heating positions P3 at positionscorresponding to the radial rack 111 of the jig 100 placed upstream.

Specifically, as shown in FIG. 9, each position detecting means 480 ismounted to a position detection rack 44 installed on the positiondetection column 43 of the heating/cooling rack 40. Each positiondetecting means 480 has a radial position detector 483 mounted to theposition detection column 43 via a first expanding/contracting mechanism481, and an axial position detector 484 mounted via a secondexpanding/contracting mechanism 482. The radial position detector 483and the axial position detector 484 are disposed perpendicular to eachother.

A first and a second expanding/contracting mechanisms 481, 482 include;a driving means for expansion/contraction 485 such as an air cylinder;and a plurality of guide rods 487 disposed in parallel with the rods 486of the driving means for expansion/contraction 485. Eachexpanding/contracting mechanism 481, 482 is prevented from falling alongthe detecting direction of each position detector 483, 484 by means ofthe rod 486 and the guide rod 487.

The radial position detector 483 and the axial position detector 484 arerespectively equipped with a rotatable and heat-resistant contactor 488coming in contact with the surface of the workpiece W, and a variationdetector 489 for detecting the amount of expansion/contraction of thecontactor 488 while pressing down the contactor 488 against theworkpiece W. As each variation detector 489, an air cylinder with alinear sensor can be used, for example.

Since the temperature of the areas to be heated H1, H2 increases duringheating, the contactor 488 is made to come in contact with positionsother than the areas to be heated H1, H2, which are being heated, fordetection. In the case of the radial position detector 483, thecontactor 488 is made to come in contact with the intermediate positionon the outer peripheral surface of the workpiece W, and the position onthe surface of the workpiece W along the radial direction from therotation center C of the workpiece W is detected. In the case of theaxial position detector 484, the contactor is made to come in contactwith an outside position of the top surface of the workpiece W placed onthe jig 100, and the position of the surface of the workpiece along theaxis line forming the rotation center C of the workpiece W is detected.

While heating is performed, the contactor 488 of the radial positiondetector 483 and that of the axial position detector 484 of eachposition detecting means 480 are made to come in contact with theworkpiece W. When the workpiece W is rotated, the contactors 488contacting the surface expand or contract while rotating, depending onthe displacement of the surface of the workpiece W. For example, bymeasuring the amount of expansion/contraction of the contactors 488 witha given position in the circumferential direction of the workpiece Wused as a reference position, the amount of displacement from thereference position is detected at each position in the circumferentialdirection of the workpiece W. Since the workpiece W is in a shape of aring, one turn allows the workpiece W to return to the originalposition.

In this way, by detecting the amount of displacement of the contactors488 by the variation detector 489, the displacement in vertical andhorizontal directions on the surface of the workpiece W is detected, andsignals indicating measurement positions are output.

[Heating Coil]

The heating coils 451 are formed in a size facing a portion of theentire length along one direction of the areas to be heated H1, H2, andplaced facing a portion of the workpiece W disposed at the heatingposition P3, of its entire circumference. The heating coils 451 of eachheating unit 450 are arranged over the entire length of the areas to beheated H1, H2 uniformly at given intervals from each other.

The shape of the heating coils 451 is selectable arbitrarily from theshapes corresponding to the arc shape of the heating region of theworkpiece W in planer view and having vertical cross-sectional shapecorresponding to the vertical cross-sectional shape of the workpiece W.In this embodiment, a plurality of heating coils 451, favorably all theheating coils 451, are in the same shape.

For example, the heating coils 451 may be in a shape where a material ina shape of a pipe, rod, or plate having approximately uniform crosssection is made to snake up and down in a given area in thecircumferential direction of the workpiece W. Specifically, as shown inFIG. 20 (a), the heating coils may be in a zigzag shape formed byconnecting square pipes so that the hollow center continues over theentire length, providing an inlet 451 b and an outlet 451 c for coolingliquid at both ends, and allowing the regions facing the workpiece W tobend at a plurality of bending portions 451 d. As shown in FIG. 20 (b),they may be in a zigzag shape formed by allowing a pipy coil materialhaving a round cross section to curve at a plurality of curving portions451 e.

As heating coils 451 used for a case where the peripheral length of theareas to be heated H1, H2 is different between the inner and outersides, those as shown in FIG. 20 (c) may be used. The portion of thisheating coil 451 facing the workpiece W may be made of a square pipe.The heating coils may be formed by bending the square pipe at aplurality of bending portions 451 f in the inner and the outer sides andat the bending portions 451 g provided between the bending portions 451f to form it in a zigzag shape. With this heating coil 451, the lengthin the circumferential direction in regions far away from the rotationcenter C may be made to be longer than the length in the circumferentialdirection in the regions closer to the rotation center W.

With such heating coils 451, to heat each area to be heated H1, H2 moreuniformly, it is desirable that the gap between the heating coils 451and the areas to be heated H1, H2 be uniform as far as possible acrossthe entire length. To achieve this, it is desirable that the shape ofthe areas to be heated H1, H2 and the shape of the surface of theheating coils 451 facing the areas to be heated H1, H2 be identical in arange as wide as possible. It is also desirable that the area of theheating coils 451 facing the areas to be heated H1, H2 be uniform as faras possible along the width direction of the areas to be heated H1, H2.Furthermore, it is preferable that the angle formed by the surface ofthe heating coils 451 facing the areas to be heated H1, H2 and the areasto be heated H1, H2 in the cross section perpendicular to the areas tobe heated H1, H2 is as small as possible, favorably 0 degrees.

The width of the heating coils 451 in the direction perpendicular to theareas to be heated H1, H2 is preferably the same as the width of theareas to be heated H1, H2. If the width of the heating coils 451 isnarrow, by displacing the disposition of the plurality of heating coils451 in the width direction, the areas to be heated H1, H2 can be heateduniformly across the entire width.

In this embodiment, the surface of the heating coils 451 facing theareas to be heated H1, H2 has a shape corresponding to the areas to beheated H1, H2, and their width perpendicular to the areas to be heatedH1, H2 is slightly narrower than the width of the areas to be heated H1,H2.

[Power Feeding Equipment]

Before the power feeding equipment 700 is explained, induction heatingdevice circuits applicable to various workpieces will be explained. FIG.11 is a circuit diagram of an induction heating device 1 according tothe embodiment of the present invention. As shown in FIG. 11, theinduction heating device 1 according to the embodiment of the presentinvention includes: a plurality of transformers 12 connected to heatingcoils 2 in parallel; a plurality of matching units 13 connected to anyone of the plurality of transformers 12; an inverter 14 connected to anyone of the plurality of matching units 13; an inverter control unit 15for controlling the inverter 14; a group of switches 16 for connectingthe inverter 14 and the matching units 13, the matching units 13 and thetransformers 12, and transformers 12 and the heating coils 2 byswitching; a switching control unit 17; and a setting unit 18.

The inverter 14 is connected to a commercial power supply 19, andincludes: a rectifier unit 14A for converting commercial voltage into DCvoltage; and an inverter unit 14B for converting the DC voltage from therectifier unit 14A into an AC voltage having a specified frequency.

The inverter control unit 15 includes: a rectification control unit 15Afor controlling the rectifier unit 14A and a plurality of inversioncontrol units 15B for controlling the inverter unit 14B. Each inversioncontrol unit 15B separately controls the inverter unit 14B to obtainvoltages having different frequencies and output them from the inverterunit 14B.

The plurality of matching units 13 include matching units 13A, 13B, and13C having different capacities. The matching units 13A, 13B, and 13Cmay include an inductance, in addition to a capacitor.

The plurality of transformers 12 are configured to include: a primarywinding connected to the matching units 13 via switches 16B, and 16C;and a secondary winding connected to the heating coil 2 via switch 16A.Each transformer 12 has different primary winding/secondary windingratios.

The group of switches 16 include: three switches 16A, for example, forconnecting the heating coil 2 and any one of the plurality oftransformers 12; three pairs of switches 16B and 16C for connecting anyone of the plurality of transformers 12 and any one of the plurality ofmatching units 13; three switches 16D, for example, for connecting anyone of the plurality of matching units 13 and the inverter 14; and threeswitches 16E, for example, for connecting any one of the plurality ofinversion control units 15B and the inverter unit 14B.

The setting unit 18 divides induction heating time into divisions, andby the division, sets frequency setting information of the voltageoutput from the inverter 14 as well as the information for selectingmatching circuits, namely combinations of the plurality of matchingunits 13 and the plurality of transformers 12, as induction heatingconditions.

According to the induction heating conditions set by the setting unit18, the switching control unit 17 selects any one of the plurality ofinversion control units 15B, controls the inverter unit 14B, and outputsa voltage having a specified frequency for each division of theinduction heating time. At the same time, the switching control unit 17connects a matching unit 13 to the inverter 14 via the group of switches16, namely switches 16A, 16B, 16C, and 16D, connects this matching unit13 to a transformer 12, and connects this transformer 12 to the heatingcoil 2.

As a monitor displaying output status from the inverter 14, the settingunit 18 is provided with a touch panel for an input/output operationscreen for setting various induction heating conditions. FIG. 12 is adrawing of a step data setting screen displayed in the setting unit 18as shown in FIG. 11. On the operation unit 18, a step data settingscreen, for example, as shown in FIG. 12 is displayed. On this step datasetting screen, a step time, a workpiece rotation rate, and a power anda voltage as output conditions from the inverter 14 can be set by thestep. On this step data setting screen, the frequency of the poweroutput from the inverter 14 may also be set.

To set a state where power is not fed from any one of the inverters 14in a specific step, the output power and the voltage from the inverter14 can be set at zero or low values, and the switching between matchingcircuits, namely combinations of transformers 12 and matching units 13,can be selected. FIG. 13 is a drawing showing the screen for settingcircuit setting conditions displayed in the setting unit 18 shown inFIG. 11. If “matching circuit switching” is selected on the screen shownin FIG. 12, a circuit setting condition screen as shown in FIG. 13appears, and on that screen the type of transformers 12 and that ofmatching units 13 can be selected. For example, as shown in FIG. 13,“MTr voltage selection” options for selecting number of turns to selecttransformers, “capacitor capacity” options for selecting matching units,and inversion control unit options are displayed as a circuit settingcondition select screen for each of the number the heating coils 2. And,these options can be selected to make the setting. On the screens asshown in FIG. 12 and FIG. 13, the frequency of AC current output fromthe inverter 14 is set by selecting an inversion control unit under thecircuit setting conditions as shown in FIG. 13. It is also possible toprovide a new column on the rightmost side on the step data settingscreen as shown in FIG. 12, and to set the frequency to be output ateach step. To switch matching circuits and frequencies, it is not alwaysnecessary to set the output from the inverter 14 to zero. It is onlynecessary to decrease the output level from the inverter 14, forexample.

According to the induction heating device 1 of the embodiment of thepresent invention, by adopting such a circuit configuration, since theinduction heating time can be divided into divisions by the setting unit18 and the inversion control unit 15B can be selected, then the voltageshaving different frequencies can be output before and after theselection. In addition, by selecting a combination of switches 16A to16D, combinations of the matching units 13 and the transformers 12 canbe switched. Consequently, by varying the output frequency of theinverter 14 and changing the combinations of the matching units 13 andthe transformers 12 in the process of increasing the temperature of theworkpiece W by the use of induction heating, the power output from theinverter 14 can be used for induction heating of the workpiece W even ifthe magnetic permeability of the workpiece W changes. Note that it isnot always necessary to change the selection of inversion control units15B when heating the same workpiece W.

The case where the temperature of a workpiece is increased to a desiredlevel by induction heating performed for relatively long time using theinduction heating device 1 as shown in FIG. 11 will hereafter beexplained. FIG. 14 is an explanatory drawing exhibiting that inductionheating can be performed for relatively long time by the inductionheating method according to the embodiment of the present invention. Theoutput frequency from the inverter 14 is unchanged during heating unlikethe device as shown in FIG. 11. Namely, it is a chart showing thetemperature of the workpiece, output impedance of the inverter 14, andthe output of the inverter 14 assessed by DC voltage obtained wheninduction heating was performed in relatively short time. FIG. 14 showsthat the output impedance from the inverter 14 decreases with time tothe minimum value, and then the output impedance starts to remainconstant when the temperature of the workpiece W increases toapproximately 70□C to 800□C. When the output impedance ceases toincrease, the output voltage from the inverter 14 hits the peak, andthen decreases. Therefore, the output from the inverter 14 is notsubsequently applied to the workpiece.

However, in the embodiment of the present invention, the outputfrequency of the impedance 14 can be changed depending on the heatingtemperature with the elapse of heating time, and this output frequencyvalue, the matching unit, and the transformer can be selected. It istherefore possible to feed induction current to the workpiece W, thusincreasing the temperature of the workpiece to a desired level, even ifthe material of the workpiece W, in particular the physical propertiessuch as a magnetic permeability should change during heating.

A typical variation of the induction heating device 1 as shown in FIG.11 will hereafter be explained. In FIG. 11, the inverter 14 may includean impedance measuring unit for measuring the output impedance. Theinverter measuring unit measures the current and the voltage output fromthe inverter unit 14B and their phase difference. The measurementresults are output from the inverter 14 to the switching control unit17. Now assume that on the step data setting screen of the setting unit18 shown in FIG. 12, “with” is selected for “switching of matchingcircuits” of step 4, for example. The switching control unit 17 ismonitoring the measurement results input from the inverter measurementunit at all times. If the impedance exceeds the current allowableimpedance range, and matching circuits are to be switched at the nextstep, the next step is forcibly entered even if the period of timespecified at the current step has not elapsed. In other words, when themeasurement result input from the impedance measuring unit is found toexceed the allowable impedance range, the switching control unit 17judges whether switching of matching circuits should be made or not byreferring to the conditions associated with the next division, of theinduction heating conditions having been set by the setting unit 18.When the matching circuits are to be switched, the switching controlunit selects the inversion control unit 15B that is to be set at thenext step forcibly, the switching control unit 17 changes the frequencyof the voltage output from the inverter 14, and switches the group ofswitches 16. Thus the frequency of the voltage output from the inverter14 is changed and at the same time matching circuits are switched toensure impedance matching.

An example where a heating unit 450, namely the induction heating device1 in this first embodiment, is configured by applying the design conceptof the induction heating device 1 as shown in FIG. 11 will be explained.

In this case, the induction heating device 1 as shown in FIG. 11 isapplied to the power feeding equipment 700 of the heating unit 450. Asshown in FIG. 11, each heating unit 450 incudes: a heating coil 451; aplurality of transformers 12; a plurality of matching units 13; aninverter 14 including a rectifier unit 14A and an inverter unit 14B; aninverter control unit 15 including a rectification control unit 15A forcontrolling the rectifier unit 14A and a plurality of inversion controlunits 15B for controlling the inverter unit 14B, thus obtainingrespective voltages having specified frequencies; and a group ofswitches 16.

As shown in FIG. 2, the heat treatment equipment 10 includes: a settingunit 31 for collectively setting induction heating conditions for eachheating unit 450; and a switching control unit 32 for switching andcontrolling the group of switches 16 of each heating unit 450 by thatsetting unit 31.

The setting unit 31 divides induction heating time into divisions, andby the division, and by heating unit 450, sets frequency settinginformation of the voltage output from the inverter 14 as well as theinformation for selecting matching circuits, namely combinations of theplurality of matching units 13 and the plurality of transformers 12, asinduction heating conditions.

Consequently, the switching control unit 32 selects any one of theplurality of inversion control units 15B and controls the inverter unit14B, thereby outputting a voltage having a specified frequency, for eachof the heating unit 450 and by the division, following the inductionheating conditions set by the setting unit 31. Furthermore, theswitching control unit 32 connects a matching unit 13 to the inverter14, connects the matching units 13 to a transformer 12, and connects thetransformer 12 to the heating coil 451, by using the group of switches16.

As a result, induction heating conditions can be set by setting unit 31for each of the heating unit 450, the output state from the inverter 14can be set, and a matching circuit can be selected by time unit from thestart of induction heating. Consequently, receiving the input of aninduction heating start signal, the switching control unit 32 controlsthe inverter 14 by the rectification control unit 15A and the selectedinversion control unit 15B of the inverter control unit 15 for each ofthe heating unit 450 with the elapse of time from the start of inductionheating, based on the induction heating conditions set in the settingunit 31. The voltage having a specified frequency is output from theinverter 14. Furthermore, by combination of selected matching unit 13and transformer 12, impedance matching corresponding to that frequencyis ensured. Consequently, even if the structure of the workpiece changesdue to induction heating, and thus its properties such as the magneticpermeability change, switches of the group of switches 16 are switchedby the switching control unit 32 in accordance with the circuit settingconditions set by the setting unit 31.

With the heat treatment equipment 10 as shown in FIG. 2 and FIG. 3, inparticular, when performing induction heating of a large workpiece W,such as an outer ring constituting a large rotating ring or an outerring constituting a large bearing having diameter of 1 m or larger,while allowing the workpiece W to travel, the entire induction heatingtime inevitably becomes long. In this case, a problem can be solved thatimpedance matching cannot be ensured as a result of change in structureof the workpiece W due to temperature increase, and thus application ofpower from the inverter 14 to the heating coil 451 becomes difficult.Even if the workpiece W is large, sufficient induction heating can beperformed to increase the temperature to a desired level. Furthermore,with the heat treatment equipment 10 shown in FIG. 2 and FIG. 3,frequency may be changed at different timing for each of the heatingunits 450 in accordance with the quenching conditions of the workpiece,or frequency may also be changed at the same timing for all the heatingunits 450.

The circuit of such induction heating device 1 can be changed asrequired within the scope of the present invention. For example, anon-contact temperature sensor can be disposed near the workpiece W, andcombinations of frequencies and matching circuits may be changed basedon the induction heating conditions set with the detection value of thattemperature sensor used as reference.

[Displacing Means]

The displacing means 460 is used to displace the relative position, andalso change the relative angle, of the workpiece W and the heating coil451.

As shown in FIG. 8, the displacing means 460 includes: a verticaldisplacing unit 462 for changing the position of the supporting box 452vertically; a horizontal displacing unit 463 for changing the positionof the supporting box 452 in the horizontal direction along the radialdirection from the rotation center C of the workpiece W; and an anglechanging unit 492 for adjusting the inclination of the supporting box452.

The vertical displacing unit 462 includes: a displacement rack 42fastened to the heating/cooling rack 40; a lower rack 464 displaced onthe displacement rack 42; and a vertical driving mechanism 465 formoving the lower rack 464 up and down with respect to the lower rack464.

The vertical driving mechanism 465 includes: a displacement guide rods466 fastened to the lower rack 464 and disposed in vertical direction;vertical displacement screw shaft 467; displacement bearings 468fastened to the displacement rack 42 and supporting the displacementguide rods 466 in vertically movable state; a vertical driving motor 469such as a servo motor fastened to the displacement rack 42; and aconnecting body 471 for moving the vertical displacement screw shaft 467up and down by the rotation of the vertical driving motor 469.

The horizontal displacing unit 463 includes: first displacement rails472 installed on the lower rack 464 in a direction approximatelyperpendicular to the radial direction of the workpiece W; an upper rack473 movable on the first displacement rails 472; a first displacementdriving mechanism 474 for moving the upper rack 473 along the firstdisplacement rails 472; second displacement rails 475 installed on theupper rack 473 along the radial direction of the workpiece W; and asecond displacement driving mechanism 476 for moving the supporting box452, which is supported in a state movable on the second displacementrails 475, along the second displacement rails 475.

The first and the second displacement driving mechanisms 474, 476respectively include; a displacement driving motor 477 such as servomotor; rotationally driven horizontal displacement screw shaft 478disposed along the first or the second displacement rails 41475 andconnected to the displacement driving motor 477; and a displacementprotrusion 479 installed on the upper rack 473 or the supporting box 452and screwed onto the horizontal displacement screw shaft 478. The firstdisplacement driving mechanism 474 need not be installed, provided thatthe heating coil 451 can be positioned in advance along the directionapproximately perpendicular to the radial direction of the workpiece W.

The angle changing unit 492 is installed in the supporting box 452, andby raising or lowering the top part of the supporting box 452 so thatthe height on the front side and that on the rear side become differentwith respect to the bottom part of the supporting box 452 supported bythe first or the second displacement rails 41475, for example, theinclination of the supporting box 452 can be changed. Although thedetailed drawing is not shown, male screws rotated by a step motor areprovided at the top and the bottom sides, and female screws screwed intothe male screws are provided on the other, to raise or lower eachposition of the supporting box 452.

By allowing the height of the supporting box 452 to become differentbetween the side of the workpiece W and the opposite side using theangle changing unit 492, the orientation of the heating coils 451 can bechanged around the shaft along one of the longitudinal directions of theareas to be heated H1, H2. In this case, the shaft along one of thelongitudinal directions is a shaft parallel to the workpiece W when theworkpiece W is in a linear shape, and it is a shaft parallel to thetangential line of the shape of the ring, when the workpiece W is in ashape of a ring.

[Posture Control Unit]

The displacing means 460 is equipped with a posture control unit 490 foradjusting the relative position and relative angle of the workpiece Wand the heating coils 451 by controlling the operation of the displacingmeans 460 based on the result of detection of the position detectingmeans 480. As shown in FIG. 8, this posture control unit 490 isintegrated into the operation unit 710 of electrical equipment, andconfigured to control each driving device of the displacing means 460.

With this posture control unit 490, by the signal showing themeasurement position of the workpiece W measured by each positiondetector 483, 484, the timing when each portion on the surface of theworkpiece W having passed each detection position passes each heatingunit 450 in immediately downstream parts and its position can beobtained, based on the amount of displacement of the workpiece W and therotation speed of the rotation driving motor 255. Consequently, bydisplacing the heating coils 451 by the displacing means 460 so as tocorrespond to the position of each portion that passes the heatingposition P3, it becomes possible to allow the position of the heatingcoils 451 to follow the workpiece W.

By the way, when areas to be heated H1, H2 of the workpiece W as shownin this embodiment are subjected to induction heating using heatingcoils 451 facing the areas to be heated H1, H2, with a specified gapmaintained, the deformation amount on one edge of the areas to be heatedH1, H2 and that on the other differ, resulting in non-uniformdeformation of the workpiece W. While a workpiece W at normaltemperature as shown by the solid line in FIG. 15 is being rotated, theareas to be heated H1, H2, namely the area between c1 and d1 on theinternal peripheral surface of the workpiece W, is heated using theheating coils 451 and the bottom side of the inner peripheral surfaceshown by the broken line in the figure is cooled using a cooling liquid.Consequently, with the temperature increase of the areas to be heatedH1, H2, non-uniform thermal expansion of the workpiece W occurs as shownin the virtual line in the figure, the deformation amount on one edge ofthe areas to be heated H1, H2 being different from that on the other. Asa result, the areas to be heated H1, H2 become the area between c2 andd2. The deformation is shown exaggerated in the figure to facilitateunderstanding.

In this case, the contactor 488 of the radial position detector 483measures a1 on the outer peripheral surface of the workpiece W whentemperature is low, and as a result of deformation of the workpiece W,measures a2 after the temperature increase. Meanwhile, the contactor 488of the axial position detector 484 measures b1 on the side peripheralsurface of the workpiece W when temperature is low, and it measures b2after the temperature increase. In other words, the measurementpositions measured as a1, b1 with the position detecting means 480 aremeasured as a2, b2 after the temperature increase. In this case, heatingis performed with the position of the heating coils 451 changed so as tocorrespond to the change in measurement positions between low and hightemperatures.

However, since the workpiece W has deformed non-uniformly, the actualareas to be heated H1, H2 have changed from the position between c1 andd1 to the position between c2 to d2. As apparent from the figure, theamount of change between c1 and c2 or between d1 and d2 is larger thanthe amount of change between a1 and a2 or between b1 and b2.

Consequently, if the workpiece W is heated using each heating coil 451based only on the measurement positions measured by the positiondetecting means 480, the heating coil 451 is disposed at a positioncorresponding to the measurement position shown by the virtual line inthe figure, and heating is performed at high temperatures in a statewhere the relative position of the heating coil 451 and the areas to beheated H1, H2 deviated non-uniformly. Furthermore, the upper edge of theareas to be heated H1, H2 on the side where distance from the heatingcoil 451 is longer, the volume of the workpiece W is larger, and theheat capacity is larger, than that of the lower edge. As a result, whenthe lower edge of the areas to be heated H1, H2, has been heated to adesired temperature, the upper edge may not be heated to a desiredtemperature, meaning that the areas to be heated H1, H2 cannot be heateduniformly.

To prevent such non-uniform heating of the areas to be heated H1, H2,the heat treatment equipment 10 in this embodiment is provided with afunction to ensure uniform heating by adjusting the position andinclination of the heating coils 451 based on the heating conditions ofthe workpiece W and the heating state during the heating period.

Heating conditions in this case include the shape, size, and material ofthe workpiece W, shape and area of the heating coils 451 facing theworkpiece, traveling speed of the workpiece W, the voltage, the current,and the frequency of the high-frequency power to be fed to the heatingcoils 451, cooling position of the workpiece W at the time of heating,and cooling liquid temperatures etc Heating state includes the surfacetemperature of the areas to be heated H1, H2, and elapsed heating time.

This posture control unit 490 adjusts the position and inclination ofthe heating coils 451 in appropriate heating state, preferably inpredetermined heating state, after induction heating is started usingthe heating coils 451 under the predetermined heating conditions. As aresult, it is made possible to heat the entire areas to be heated H1, H2as uniformly as possible. The decrease in heating efficiency due tonon-uniform width of the gap, etc. with respect to supplied power can beprevented.

Specifically, the following function is provided.

First, the results of detection by each position detecting means 480 atthe time of heating, namely the measurement positions obtained by thedetection result measured at positions other than the areas to be heatedH1, H2, are corrected at least based on the shape of the workpiece, andthe operation of the displacing means 460 is controlled so as tocorrespond to the corrected positions obtained by the correction.

It is preferable that the reference position is the one where thedistance between the area of the heating coils 451 facing the areas tobe heated H1, H2 and the surface of the areas to be heated H1, H2becomes a specified value, provided that the gap between the heatingcoils 451 and the areas to be heated H1, H2 is uniform over the entirelength of the heating coils 451.

If the gap between the heating coils 451 and the areas to be heated H1,H2 becomes non-uniform, a position can be selected where the distancebetween a given position on the face of the heating coils 451 facing theareas to be heated H1, H2 and a position on the areas to be heated H1,H2 corresponding to that position becomes a given value.

In this embodiment, the measurement positions detected by the radialposition detector 483 and the axial position detector 484 of theposition detecting means 480 are displacement from the referenceposition respectively. The corrected positions are correcteddisplacement obtained by correcting the measured displacement. Thisposture control unit 490 controls the operation of the displacing means460 so as to correspond to the corrected displacement.

To correct measurement positions, the measurement position data can becorrected using a correction coefficient. For example, the correctedposition can be found that a signal showing the measurement position ismultiplied by a correction coefficient. This correction coefficient isat least a value corresponding to the shape of the workpiece, and byusing a correction coefficient satisfying as many heating conditions aspossible, the heating coils 451 can be arranged more accurately on theareas to be heated H1, H2.

Such a correction coefficient may be the one obtained by experience. Or,the deformation of the workpiece W at set heating state during heatingmay be calculated based on heating conditions, set heating state, etc.,and a correction coefficient can be found based on the deformationamount of the region measured by the radial position detector 483 andthe axial position detector 484 of the position detecting means 480 andthe amount of displacement of the areas to be heated H1, H2 found bycalculation. Furthermore, a step of simulation processing for finding acorrection coefficient can be set in the posture control unit 490 inadvance, and the correction coefficient may be found by this simulationprocessing. Such a correction coefficient may be input at the time ofheating or before heating, or may be stored in the posture control unit490.

It is preferable that this correction coefficient is made to bedifferent between the time when temperature is low and when it is high.It can be changed manually or automatically when the set heating statehas been reached, when the temperature of the areas to be heated H1, H2has reached the set heating state such as from 700□C to 800□C, forexample, or when predetermined time has elapsed after the start ofheating.

The posture control unit 490 in this embodiment also has a function ofdisplacing the position of some of, or all of, the plurality of heatingcoils 451 during heating period.

By allowing the displacing means 460 to displace the position of eachheating coil 451 by the control of the posture control unit 490, theadjustment is made so that the area where the plurality of heating coils451 and the areas to be heated H1, H2 face each other changes in thewidth direction of the areas to be heated. For example, at the time ofstart of heating, each heating coil 451 is made to be disposed atapproximately the same positions in the width direction of the areas tobe heated H1, H2 of the workpiece W, and when a specified heating stateis reached, the position of each heating coil 451 in the width directionof the areas to be heated H1, H2 is displaced individually, or incombination of two or more heating coils. All the heating coils 451 maybe displaced.

The disposition and the amount of displacement of the plurality ofheating coils may be determined based on experience, or may bedetermined so that they correspond to the gap between each heating coil451 and the areas to be heated H1, H2 or the change in the gap duringthe heating period. Or, the deformation of the workpiece W in setheating state at the time of heating may be calculated based on theheating conditions, set heating state, etc., and the disposition and theamount of displacement may be determined so as to correspond to thecalculation result. Or they may be determined so that larger area of theheating coils 451 is disposed on the lower temperature side, in responseto the temperature distribution in the width direction of the areas tobe heated H1, H2. Furthermore, it is also possible to set a step ofsimulation processing for determining the disposition of the pluralityof heating coils 451 in the posture control unit 490 in advance, anddetermine them by this simulation processing. In this case, thedeformation amount in the width direction of the areas to be heated H1,H2 is found by simulation processing, and the area may be adjusted so asto correspond to this deformation amount, or selection may be made fromthe compiled data on the disposition.

To displace the heating coils 451 during the heating period, some of allthe heating coils 451 may be disposed by displacing them to the edgeside. Or the disposition obtained by displacement may be stored inaccordance with the set heating conditions in advance, and displacementmay be performed manually or automatically when the set heatingconditions are satisfied.

In a state where the disposition of each heating coil 451 is displaced,it is also possible to dispose a part of different heating coils 451 maybe disposed at the same position in the width direction of the areas tobe heated H1, H2, and the same position in the width direction of theareas to be heated H1, H2 may be heated in superposed state.

As a result, the disposition/distribution of the plurality of heatingcoils 451 in the width direction of the areas to be heated H1, H2 can beadjusted to differ between before and after the displacement of theheating coils 451, thus making it possible to adjust the amount ofheating due to induction heating properly.

Then, the posture control unit 490 in this embodiment has a function ofchanging the posture of the supporting box 452, thus adjusting theposture, namely the angle of the heating coils 451 relative to the areasto be heated H1, H2, so that the face of the heating coils 451 facingthe areas to be heated H1, H2 is placed along the areas to be heated H1,H2 during the heating period. In this case, adjustment is made so thatthe angle formed by the face of the heating coils 451 facing the areasto be heated H1, H2 and the areas to be heated H1, H2 is minimized oreliminated during the heating period. If the shape of the face of theheating coils 451 facing the areas to be heated H1, H2 is different fromthe shape of the areas to be heated H1, H2, it is desirable that theangle formed by the face of the heating coils 451 facing the areas to beheated H1, H2 and the areas to be heated H1, H2 be made to be as smallas possible.

The amount of adjustment of the posture of the heating coils 451 may bedetermined based on experiences. It can also be made to correspond tothe gap between the areas to be heated H1, H2 and each heating coil 451or to the change in the gap during heating period. Or deformation of theworkpiece W in set heating state during heating may be calculated basedon heating conditions, set heating state, etc., and the amount ofadjustment may be determined so that it corresponds to the calculationresult. It is also possible to determine the amount of adjustment sothat the heating coils 451 come closer to the areas to be heated H1, H2on the low temperature side, corresponding to the temperaturedistribution in the width direction of the areas to be heated H1, H2.

Furthermore, it is also possible to set a step of simulation processingto determine the posture of the plurality of heating coils 451 in theposture control unit 490 in advance, and determine the amount ofadjustment by this simulation processing. In this case, the deformationamount in the width direction of the areas to be heated H1, H2 may befound by the simulation processing, and the amount of adjustment of theposture may be determined so that it corresponds to this deformationamount.

To adjust the posture of the heating coils 451 by changing itsorientation during the heating period, the posture control unit 490 maybe operated during the heating period based on experiences. In addition,the posture may be stored in advance in accordance with the set heatingconditions, and the orientation may be changed manually or automaticallywhen the set heating conditions are satisfied.

As shown in FIG. 16, the posture control unit 490 in this embodimentincludes: a setting input unit 493 for inputting the heating conditionsand the set heating state of the workpiece W; an arithmetic processingunit 494 for calculating the amount of control of the displacing meansbased on the heating conditions and set heating state of the workpieceW; a storage unit 495 for storing various settings input to the settinginput unit 493 and calculation results obtained by the arithmeticprocessing unit; a heating state evaluating unit 496 for evaluating thatthe heating state of the areas to be heated H1, H2 has reached the setheating state; and a driving control unit 497 for driving the displacingmeans 460 when the set heating state is reached. In this case, elapsedheating time is used as heating state, but it is also possible to usethe temperature of the areas to be heated H1, H2 as the heating state.

In that case, as shown by the broken line in FIG. 16, the temperature ofthe areas to be heated H1, H2 may be detected using a non-contacttemperature sensor, and the set heating state may be judged to have beenreached when the heating state evaluating unit 496 judges that thetemperature set in advance has been reached.

The storage unit 495 stores the steps for displacing the heating coils451 after the start of heating, following the position of the workpieceW in the heating position P3, based on signals from the positiondetecting means 480. Heating conditions and informations for adjustingthe position and the angle of the heating coils 451 relative to theareas to be heated H1, H2 are stored in combination with the set heatingstate. They may be those input at the setting input unit 493, or thosefound by calculation.

Furthermore, the storage unit 495 stores the processing step informationused for simulation processing.

Simulation processing steps are for calculating the state of deformationwhen the areas to be heated H1, H2 have reached the set heating stateunder the heating conditions, and their methods are not limited to anyspecific ones. For example, simulation processing where thermaldeformation is found as an analytical model by the two-dimensionalfinite element method (FEM) may be used.

[Power Adjusting Means]

The power adjusting means 491 is set as a part of the operating unit 710of the power feeding equipment 700. This power adjusting means 491adjusts the high-frequency power to be fed to the plurality of heatingcoils 451 separately for each of the heating coils 451. Thehigh-frequency power may be adjusted to the value that has been setcorresponding to the set heating state, when or after the predeterminedset heating state is reached.

In combination with the adjustment by the posture control unit 490 ofthe position and angle of each heating coil 451 relative to the areas tobe heated H1, H2, this power adjusting means 491 varies thehigh-frequency power to be fed to each heating coil 451, thus allowingthe plurality of heating coils 451 to heat the areas to be heated H1,H2.

[Cooling Section]

As shown in FIG. 10, the cooling section 500 includes: a water tank 510installed below the heating section 400; and a plurality of coolingjackets 520 as cooling units disposed within the water tank 510, and itis capable of stably supporting the radial racks 111 of the jig 100.

The water tank 510 is installed, surrounding the jig 100 and theworkpiece W, to prevent cooling liquid from splashing. The plurality ofcooling jackets 520 are disposed, facing the workpiece W and at aplurality of positions in the circumferential direction of the workpieceW at mostly regular intervals, so that a large amount of cooling liquidcan be discharged to the workpiece W and contact the workpiece W.

[Heat Treatment Method]

A method of heat-treating a workpiece W using such heat treatmentequipment 10 will hereafter be explained.

With the heat treatment method in this embodiment, a preparation processfor setting each part depending on the workpiece W, a bring-in processfor bringing in the workpiece W and mounting it onto a jig 100, and atransfer process for transferring the jig 100 carrying the workpiece Ware followed, and then heat treatment of one of the areas to be heatedH1, H2 is performed. The heat treatment includes: a heating process forinduction-heating the workpiece W on the jig 100; and a cooling processfor cooling the workpiece W on the jig 100. Then the heat-treatedworkpiece W is discharged in the subsequent discharge process.

In the preparation process, setting of each part is made depending onthe size and the shape the workpiece W to be heated. To mount thecomponents of the heating unit 450 such as heating coils 451 to theheating unit 450, parts replacement section 600 and parts replacementjig 620 as shown in FIG. 2 and FIG. 3 can be used.

In the bring-in process, the workpiece W to be heated is brought in bythe bring in/out section 300 as shown in FIG. 2 and FIG. 3, and placedon the jig 100 to be ready for being transferred.

At the bring in/out position P1 of the bring in/out section 300, the jig100 is made to support the workpiece W. As shown in FIG. 4, theworkpiece W is placed on a plurality of rotating rollers 112 of the jig100 in a manner surrounding the central structure 130, with one edgeface facing downward. Then the jig 100 carrying the workpiece W istransferred to a suspending position P2 and stopped.

In the transfer process, as shown in FIG. 3 and FIG. 4, the jig 100carrying the workpiece W is connected to the transfer loader 220 of thetransfer mechanism 200, and transferred to the heating section 400 inhoisted state.

In the heating process, the jig 100 is disposed in the specifiedposition in the heating section 400 as shown in FIG. 2 and FIG. 8, andby disposing the jig 100 while controlling its move in the vertical andcircumferential directions, the workpiece W placed on the jig 100 isdisposed on each heating position P3, and one of the areas to be heatedH1, H2 is heated. Either one of the areas to be heated H1, H2 may beheated.

In the heating process, heat treatment steps as shown in FIG. 17 areexecuted.

First, prior to the start of heat treatment, heating conditionsdescribed previously are input from the setting input unit 493 in theinput process S1. This input can be made on the touch panel of theoperating unit 710 or from a mobile terminal 701. A desired item isselected on the main menu as shown in FIG. 5, and on the entry screen,various heating conditions are entered. In this case, one or a pluralityof set heating states are set in advance, considering expected increasein positional displacement between the measurement positions measured bythe position detecting means 480 and the actually heated areas to beheated H1, H2 of the workpiece W due to increase in non-uniformdeformation of the workpiece W.

In the simulation process S2, the arithmetic processing unit 494performs simulation processing based on the entered heating conditions,following the simulation processing steps stored in the storage unit495. In this processing, the correction coefficient in each set heatingstate, the disposition of each of the plurality of heating coils 451 inthe width direction of the areas to be heated H1, H2, and theinclination of each heating coil 451 are calculated, and each of theobtained calculation results are stored in the storage unit 495 in astate corresponding to each set heating state.

After the simulation process S2, in a state where the workpiece W isplaced at each heating position P3 in the treatment starting process S3,the rotating roller 112 is rotated to allow the workpiece W to rotatealong the ring shape, and the circumferential speed of the workpiece Wis maintained constant by the rotation driving unit 30. As shown in FIG.9, the contactors 488 of the position detectors 483, 484 are made tocontact the middle and the upper face on the outer peripheral surface ofthe workpiece W to measure the measurement positions. As shown in FIG.8, cooling liquid is injected from an auxiliary cooling unit 440 to thelower side adjacent to the areas to be heated H1, H2 to start cooling.

The displacing means 460 is actuated by the control of the posturecontrol unit 490 to displace the heating coils 451 so that the heatingcoils 451 are disposed facing the areas to be heated H1, H2 while aspecified gap is maintained. In this case, when the heating is started,the deformation of the workpiece W and the measurement positionsmeasured by the position detecting means 480 are approximatelycoincided, and consequently, correction coefficient can be 1.Furthermore, since the heating coil 451 is supported by the supportingbox 452 so that its inclination corresponds to the inclination of theareas to be heated H1, H2 in the width direction, the supporting box 452of the displaying means 460 is in an approximately horizontal state,meaning that there is no difference in relative angle between theheating coils 451 and the areas to be heated H1, H2. In addition, theplurality of heating coils 451 may be arranged around the central lineof the areas to be heated H1, H2 in the width direction.

In this state, the inducting heating treatment process S4 is started. Inthe induction heating treatment process S4, while measurement ofrotation, cooling and measurement positions of the workpiece W iscontinued, high-frequency power is fed to the heating coils 451 tosubject the areas to be heated H1, H2 to induction heating.

By detecting the amount of displacement of the contactors 488 of theradial position detector 483 and the axial position detector 484 of eachposition detecting means 480 using a variation detector 489, themeasurement position of the areas to be heated H1, H2 at each heatingposition P3 is measured. As a result, heating can be performed whileeach heating coil 451 is made to follow the workpiece W. For example,even in a case where the workpiece W is rotated while its position isdisplaced in the radial direction because the workpiece W is disposedeccentrically with respect to the center of the jig 100 and otherreasons, the heating coil 451 can be made to follow the workpiece W forheating.

In this induction heating treatment process S4, the heating state iscontinuously detected after the start of heating, and the elapsedheating time after the start of heating is detected as the heatingstate.

Because the workpiece W is large and heating is performed using theplurality of heating coils 451 disposed at intervals in thecircumferential direction, the heating period of the induction heatingtreatment process S4 may become as long as several minutes. During thisheating period, the heating state and the position of the workpiece Ware monitored, and workers can check them on the monitor screen, etc. ofthe operating unit 710 or the mobile terminal 701.

As a result of performing the induction heating treatment as describedabove continuously, the areas to be heated H1, H2 and the workpiece Ware heated. At the same time, the workpiece W is deformed gradually andnon-uniformly due to thermal expansion.

When the heating state is then judged to have reached to the set heatingstate by the heating state evaluating unit 496, the arithmeticprocessing unit 494 changes the correction coefficient to the one in theset heating state stored in the storage unit 495. By using thiscorrection coefficient, the measurement position measured by theposition detecting means 480 is corrected to calculate the correctedposition. As a result, in a high-temperature state after the set heatingconditions are satisfied, following operation is performed, with theposition of the areas to be heated H1, H2 at each heating position P3regarded as corrected position, until the next set heating conditionsare satisfied. Namely, the operation of the displacing means 460 arecontrolled by the posture control unit 490 to allow it to correspond tothe change in the corrected position, and thus the relative position ofthe heating coil 451 and the areas to be heated is maintained stably.

When the heating state is judged to have reached to the set heatingstate, the arithmetic processing unit 494 finds the amount of controlthat allows the inclination of each heating coil 451 in set heatingstate stored in the storage unit 495 to be ensured, and the posturecontrol unit 490 controls the operation of the displacing means 460based on that amount of control. By allowing an angle changing unit 492to raise or lower the top part of the supporting box 452 so that itsheight becomes different between the front and the rear sides, theinclination angle of the surface of the heating coils 451 facing theareas to be heated H1, H2 is adjusted to coincide with the inclinationangle of each heating coil 451 in the set heating state.

For example, as shown in FIG. 18, until the set heating state isreached, each heating coil 451 is arranged, inclined as shown by thesolid line in the figure. After the set heating state is reached, sincethe inclination of the areas to be heated H1, H2 changes due tonon-uniform deformation of the workpiece W, the inclination is made tochange by angle □ as shown by the virtual line in the figure so as tocorrespond to this change to make the gap between each heating coil 451and the areas to be heated H1, H2 more uniform.

In the high-temperature state after the set heating conditions aresatisfied, this angle is maintained until the next set heatingconditions are satisfied.

Further, when the heating state is judged to have reached the setheating state, the arithmetic processing unit 494 finds the amount ofcontrol that allows the inclination of each heating coil 451 in setheating state stored in the storage unit 495 to be ensured, and theposture control unit 490 controls the operation of the displacing means460 based on that amount of control. In this case, since the edge of theareas to be heated in the width direction, the top edge in particular,changes its position in a direction apart from each heating coil 451 dueto non-uniform deformation of the workpiece W, for example, the surfacetemperature of the areas to be heated H1, H2 becomes non-uniform, thustending to become lower than the temperature of the intermediate part,because the calorific value due to induction heating tends to becomelower than that of the intermediate part.

Consequently, as shown by the solid line in FIG. 19, whereas theplurality of heating coils 451 are disposed uniformly in the widthdirection of the areas to be heated H1, H2 before the set heating stateis reached, some of the plurality of heating coils 451 are disposed,deviated toward the edge of the areas to be heated H1, H2 as shown bythe virtual line in the figure. All of the plurality of heating coils451 may be disposed, deviated toward the edge, as required. As a result,distribution of the areas of the heating coils 451 facing the areas tobe heated H1, H2 in the width direction is adjusted, and each heatingcoil 451 is disposed so that the areas facing each other become largeron the low-temperature side of the areas to be heated H1, H2 to increasethe calorific value on the low-temperature side.

In the high-temperature state after the set heating conditions aresatisfied, this angle is maintained until the next set heatingconditions are satisfied.

By performing such control once or performing it repeatedly, theinduction heating treatment process S4 is followed until heatingcomplete state is reached, and thus the entire areas to be heated H1, H2are heated uniformly. When the temperature of the areas to be heated H1,H2 has reached a desired temperature, or when the predetermined heatingtime has elapsed, the induction heating treatment process S4 iscompleted.

In the cooling process after the induction heating treatment process S4is completed, the jig 100 is lowered by the transfer loader unit 220,the workpiece W on the jig 100 is placed in the cooling section 500, anda large amount of cooling liquid is injected to the workpiece W from thecooling jackets 520 installed at a plurality of positions to cool theentire workpiece W. In this case, since the cooling section 500 isinstalled below the heating section 400, cooling is started in a shorttime after the heating, and thus a desired heat treatment of theworkpiece W is performed.

When the temperature of the areas to be heated H1, H2 have decreasedsufficiently, the cooling process is completed. The heat treatment ofone of the areas to be heated H1, H2 has thus completed.

Then the workpiece W having undergone heat treatment is suspended in thetransfer loader unit 220 along with the jig 100, and it is transferredto the bring in/out section 300. Heat treatment of the workpiece W isthus completed.

[Functional Effect in the Embodiment]

According to the heat treatment equipment 10 and the heat treatmentmethod as described above, the deformation amount that appears on oneedge of the areas to be heated H when the workpiece W isinduction-heated differs from that on the other. Consequently, even ifthe error of the measurement positions detected by the positiondetecting means 480 increases, the measurement positions are correctedbased on the shape of the workpiece, and the relative position of theworkpiece W and the heating coils 451 is adjusted. The temperature ofthe entire areas to be heated H1, H2 can thus be increased to a desiredlevel uniformly.

In this case, the posture control unit 490 is equipped with anarithmetic processing unit 494 for calculating the corrected positionsbased on the measurement positions and correction coefficient, andarithmetic processing unit 494 finds the correction coefficient bypredetermined simulation processing for the case where heating treatmentof the workpiece W is performed under the heating conditions that are tobe followed. Consequently, there is no need to make preparations todetermine correction coefficient, and thus provision of devices forheating the workpiece W or the time and efforts can be minimized.

The measurement positions are measured as deviations from the referenceposition, and the corrected positions are the corrected deviationsobtained by correcting the measured deviations. The posture control unit490 controls the operation of the displacing means 460 to eliminate thedeviation in correction. As a result, the data showing the measurementpositions and corrected positions can be simplified, and the structurefor measuring the measurement positions by the position detecting means480 or the structure for transferring the heating coils 451 to correctedpositions by the displacing means 460 can be simplified. In addition,the processing speed can be improved and the heating coils 451 can thusbe placed in appropriate positions in a shorter time, and the areas tobe heated H1, H2 can be heated efficiently.

The corrected positions are those obtained by correcting the measurementpositions using a correction coefficient at least corresponding to theshape of the workpiece W. Consequently, the corrected positions can becalculated easily. The posture control unit 490 changes the correctioncoefficient when the predetermined set heating state of the areas to beheated H1, H2 is reached during the heating period. As a result, even ifthe amount of non-uniform deformation of the workpiece W increases withthe increase in temperature, the heating coils 451 can be disposed inappropriate positions.

According to the heat treatment equipment 10 and the heating method asdescribed above, even if the deformation amount that appears on one edgeof the areas to be heated H when the workpiece W is induction-heateddiffers from that on the other, the heating coils 451 are disposed inappropriate positions. It is because that the heating coils 451 arearranged along the areas to be heated H at the time of heating, and notalong the areas to be heated H before the heating. Consequently, theareas to be heated H, whose temperature has increased, can be heatedsufficiently using the heating coils 451. Thus the temperature of theentire areas to be heated H can be increased uniformly to a desiredlevel.

In this case, the arithmetic processing unit 494 is provided tocalculate the relative angle between the surface of each heating coil451 facing the areas to be heated H and the areas to be heated in theset heating state of the areas to be heated H. It is therefore possibleto find the relative angle automatically from detection result, etc.

Furthermore, since this relative angle is calculated by predeterminedsimulation processing, the preparation of finding the relative angle inadvance is unnecessary, minimizing the time and the labor of the heattreatment.

The displacing means 460 is provided to change the angle of the heatingcoils 451 facing the areas to be heated H relative to the areas to beheated H around the axis along one direction. Namely, it is possible tochange the orientation of the heating coils 451 easily along thedirection of change in the areas to be heated H during heating. The gapbetween the surface of the heating coils 451 facing the areas to beheated H and the areas to be heated H of the workpiece W can thus bemade to be uniform easily.

The posture control unit 490 is provided to control the operation of thedisplacing means 460. The adjustment is made by this posture controlunit 490 so that the difference in angle between the surface of theheating coils 451 facing the areas to be heated H and the areas to beheated H is eliminated during heating. As a result, the orientation ofthe heating coils 451 can be changed easily.

According to the heat treatment equipment 10 and the heating method asmentioned above, by providing a displacing means 460 for separatelychanging the positions of the plurality of heating coils 451 in thewidth direction of the areas to be heated H, and allowing thisdisplacing means 460 to change the position of each heating coil 451,disposition/distribution of the plurality of heating coils 451 in thewidth direction of the areas to be heated H is adjusted. The regionheated by induction heating can thus be adjusted for each of the heatingcoils 451. As a result, the calorific value distribution in the widthdirection of the areas to be heated H can be adjusted, the temperatureof the areas to be heated H is prevented from becoming non-uniform inthe width direction of the areas to be heated H, and the temperature ofthe entire areas to be heated H can be increased uniformly to aspecified level.

The power adjusting means 491 for individually adjusting thehigh-frequency power to be fed to each heating coil 451 is provided. Theareas to be heated H are heated by adjusting the position of eachheating coil 451 and at the same time varying the high-frequency powerto be fed to each heating coil 451 by this power adjusting means 491.Consequently, the calorific value distribution in the width direction ofthe areas to be heated H can be adjusted more appropriately, and thetemperature of the entire areas to be heated H can thus be increased toa specified level easily and uniformly.

Since the plurality of coils are of the same shape, a plurality ofheating coils 451 can be manufactured easily, and correction coefficientcan be manufactured at lower cost.

The posture control unit 490 is provided to control the operation ofeach displacing means 460, and the posture control unit 490 changes theposition of each heating coil 451 corresponding to the gap between theareas to be heated H and each heating coil 451. As a result, if theworkpiece W deforms non-uniformly due to temperature increase, the timeand effort for adjusting the orientation of the heating coils 451 can beminimized or eliminated.

Since the posture control unit 490 changes the position of the pluralityof heating coils 451 during the heating period, the entire width of theareas to be heated H can be heated uniformly even if the workpiece Wdeforms significantly in high-temperature state.

The above embodiment can be modified as required within the scope of thepresent invention.

For example, in the above embodiment, the measurement positions detectedby the position detecting means 480 are corrected, and at the same timethe plurality of heating coils 451 are disposed by adjusting thedisposition/distribution of the plurality of heating coils 451 in thewidth direction of the areas to be heated H1, H2, and adjusting theangle of the heating coils 451 to allow it to correspond to the areas tobe heated H1, H2 during heating. It is possible, however, to minimizethe non-uniform heating state of the areas to be heated to ensureuniform heating by more appropriately correcting the measurementpositions detected by the position detecting means 480 without adjustingthe disposition/distribution and the angle of heating coils 451. It isalso possible to minimize non-uniform heating state of the areas to beheated to ensure uniform heating by disposing the heating coils 451while adjusting their angle to allow them to correspond to the areas tobe heated H1, H2 during heating without correcting the measurementpositions or adjusting the disposition/distribution of the heating coils451. Furthermore, it is possible to minimize non-uniform heating stateof the areas to be heated to ensure uniformity by adjusting thedisposition/distribution of the plurality of heating coils 451 in thewidth direction of the areas to be heated H1, H2 more appropriatelywithout correcting measurement positions and adjusting the angle ofheating coils 451.

An example where the workpiece W and the heating coils 451 are movedrelative to each other by rotating the workpiece W with respect to theheating coils 451 was explained above. However, it is also possible toensure relative move by rotating the heating coils 451.

An example where the angle of the heating coils 451 is adjusted duringthe heating period was explained above. It is also possible to disposethe face of the heating coils 451 facing the areas to be heated H1, H2in a fixed manner in advance so as to correspond to the areas to beheated H1, H2 during the heating period.

An example where all the heating coils 451 are displaced separately bythe displacing means 460 was explained above, but the displacement ofcombinations of a plurality of heating coil 451, two heating coils forexample, is also possible.

Taking the displacement of the gap and occurrence of non-uniformtemperature distribution of the areas to be heated H1, H2 intoconsideration, the disposition of the plurality of heating coils 451 maybe adjusted in advance in order to cope with the occurrence of theabove, thus ensuring uniform heating.

The present invention is also applicable to a workpiece W where thedeformation amount that appears on one edge of the areas to be heatedH1, H2 when the areas to be heated are induction-heated is not differentfrom that on the other. Namely, by applying the present invention whilethe temperature distribution of the areas to be heated H1, H2 isnon-uniform during heating, and adjusting the disposition of eachheating coil 451, the unevenness of heating state is minimized to ensureuniform heating. An example where the width of the areas to be heatedH1, H2 and the width of the heating coils 451 are similar was explainedabove. However, the present invention is also applicable to a case wherethe heating is performed using a plurality of heating coils 451 having awidth smaller than the width of the areas to be heated H1, H2. In thiscase, when heating a workpiece W, where the entire length of the areasto be heated H1, H2 is divided into belt-like divisions having differentlengths laid next to each other in the width direction using a pluralityof heating coils 451 having a width narrower than the width of the areasto be heated H1, H2, the plurality of heating coils 451 may be disposedso that the area of the heating coils 451 facing the workpiece is setdepending on the length of the belt-like divisions. For example, moreheating coils 451 of the same shape may be disposed in longer divisionsthan in shorter ones.

Second Embodiment

A second embodiment is an example of subjecting both areas to be heatedH1, H2 of the workpiece W to heat treatment using the same heattreatment equipment as the first embodiment.

In the heat treatment method of this second embodiment, a preparationprocess, a bring-in process, and a transfer process are followed, andafter the workpiece W is transferred to the heating section 400, theheat treatment of each areas to be heated H1 H2 is performed. In thisheat treatment, the areas to be heated H1, H2 are subjected to heattreatment sequentially.

Specifically, as shown in FIG. 21, this embodiment includes: a firstheating process S11 for heating a first area to be heat-treated H1 ofthe workpiece W placed on a jig 100; a first cooling process S12 forrapidly cooling the first area to be heat-treated H1 that has beenheated; a first tempering process S13 for heating and gradually coolingthe first area to be heat-treated H1 after the first cooling processS12; next, an inversion process S14 for inverting the workpiece andplacing it on the jig 100 after the first tempering process S13. Afterthe inversion process S14, this embodiment includes: a second heatingprocess S15 for heating the second area to be heat-treated H2 of theinverted workpiece W; a second cooling process S16 for rapidly coolingthe second area to be heat-treated H2 that has been heated; and a secondtempering process S17 for heating and gradually cooling the second areato be heat-treated H2 after the second cooling process S16.

In the first heating process S11, as shown in FIG. 8 (a) and FIG. 22(b), the jig 100 is placed at a specified position in the heatingsection 400, and by disposing the jig 100 while regulating its move invertical and circumferential directions, the first area to beheat-treated H1 of the workpiece W placed on the jig 100 is disposed ateach heating position P3 for heating.

Rotation and cooling of the workpiece W are performed continuously, andat the same time, the heating coils 451 are made to follow the surfaceof the workpiece W, and high-frequency power is fed to the heating coils451 to perform induction heating of the first area to be heat-treatedH1.

By detecting the position of the workpiece W in the radial and axialdirections using each position detecting means 480, the position of thefirst area to be heat-treated H1 at each heating position P3 iscalculated. To that end, the displacing means 460 is actuated, andheating is performed while each heating coil 451 is made to follow theworkpiece W. For example, even in a case where the workpiece W isrotated while being displaced in the radial direction during turning asa result of being disposed eccentrically from the center of the jig 100,the heating coils 451 can be made to follow the workpiece W for heating.

The temperature of the first area to be heat-treated H1 increases bycontinuously performing induction heating. A cooling liquid iscontinuously sprayed to the workpiece W from the auxiliary cooling unit440 during heating to prevent the temperature of the areas other thanthe first area to be heat-treated H1, the second area to be heat-treatedH2 in particular, from increasing to heat treatment temperature.

Heating is continued until the specified heating complete state isreached to heat the entire area to be heat-treated H1 uniformly. Forexample, when the temperature of the first area to be heat-treated H1has reached a desired temperature, such as A3 transformation point or A1transformation point or higher for example, and the predeterminedheating time has expired, the first heating process S11 is completed.

In the first cooling process S12, as shown in FIG. 10 and FIG. 22 (b),the jig 100 is lowered by the transfer loader unit 220 after the firstheating process S11 is completed, the workpiece on the jig 100 isdisposed on the cooling section 500, and while the workpiece W is beingrotated, a large amount of cooling liquid is injected to the workpiece Wfrom cooling jackets 520 installed at a plurality of positions torapidly cool the entire first area to be heat-treated H1 of theworkpiece W. Tempering of the first area to be heat-treated H1 is thusperformed. In this case, since the cooling section 500 is installedbelow the heating section 400, the cooling is started in a short timeafter the heating. Desired tempering of the workpiece W is thusperformed. When the temperature of the first area to be heat-treated H1or the workpiece W has decreased to sufficiently low level, the coolingprocess is completed.

After the first cooling process S12, as shown FIG. 8 (a) and FIG. 22(c), the first tempering process S13 for heating and gradually coolingthe first area to be heat-treated H1 is performed.

In this first tempering process S13, the jig 100 as shown in FIG. 8 (a)is raised and disposed by the transfer loader unit 220, while thetransfer of the jig 100 in the vertical and the circumferentialdirections is regulated in the heating section 400, and the first areato be heat-treated H1 of the workpiece W placed on the jig 100 isdisposed at each heating position P3 and heated. During heating, all ofor some of the same heating coils 451 used in the first heating processS11 are used. While rotation and cooling of the workpiece W areperformed and the heating coils 451 are made to follow the surface ofthe workpiece W, power is fed to the heating coils 451 to performinduction heating, thus heating the surface temperature of the firstarea to be heat-treated 170□C to 200□C, for example. After thepredetermined time has elapsed, cooling is performed in the atmosphere,for example. The workpiece W is thus subjected to low-temperaturetempering, and the hard and brittle structure formed in the firstheating process S11 and the first cooling process S12 is transformedinto a tempered structure having improved toughness, for example.

Then, as shown in FIG. 10 and FIG. 22 (d), the jig 100 as shown in FIG.8 (a) is lowered again by the transfer loader unit 220, the workpiece Won the jig 100 is disposed in the cooling section 500, and while theworkpiece W is rotated, a large amount of cooling liquid is injected tothe workpiece W from the cooling jackets 520 installed at a plurality ofpositions to cool the entire workpiece W to sufficiently lowtemperature.

After the first tempering process S13 is completed, inversion processS14 where the workpiece W is inverted vertically and placed on the jig100 shown in FIG. 8 (a) is followed. In the inversion process S14, theorientation of both edges of the workpiece W is inverted. Consequently,the first area to be heat-treated H1 is placed at the bottom, whereasthe second area to be heat-treated H2 is placed at the top.

Next, the jig 100 on which the workpiece W is placed as shown in FIG. 8(a) is then transferred to dispose the second area to be heat-treated H2of the workpiece W at each heating position P3.

After the inversion process S14 is completed, a second heating processS15 for heating the second area to be heat-treated H2 of the workpiece Wis followed. Since the first area to be heat-treated H1 and the secondarea to be heat-treated H2 of the workpiece W are in plane-symmetricalshape in this embodiment, and by inverting the workpiece W, the secondarea to be heat-treated H2 can be disposed similarly to the first areato be heat-treated H1 before the inversion, the same heating coils 451used in the first heating process S11 are used in the second heatingprocess S15.

In the second heating process S15, as shown in FIG. 8 (a) and FIG. 23(a), the second area to be heat-treated H2 of the workpiece W placed onthe jig 100 is heated in the same manner as the first heating processS11. While the second area to be heat-treated H2 is heated, coolingliquid is continuously sprayed to the second area to be heat-treated H2from the auxiliary cooling unit 440 to prevent the temperature of thesecond area to be heat-treated H2 from increasing to heat treatmenttemperatures such as A1 and A3 transformation points or higher withoutfail.

After the second heating process S15 is completed, a second coolingprocess S16 is followed. In the second cooling process S16, as shown inFIG. 10 and FIG. 23 (b), the heated second area to be heat-treated H2 istransferred to the cooling section 500 immediately for rapid cooling asin the same manner as the first cooling process S12. The second area tobe heat-treated H2 is thus subjected to tempering.

In this embodiment, a second tempering process S17 is followed after thesecond cooling process S16. The second tempering process S17 is followedin the same manner as the first tempering process S13, as shown in FIG.8 (a) and FIG. 23 (c). Namely, the jig 100 is raised, the second area tobe heat-treated H2 of the workpiece W placed on the jig 100 is disposedat each heating position P3 and heated to 170□C to 200□C, for example,using all or some of the heating coils 451 used in the second heatingprocess S15, and then cooled in the atmosphere. The workpiece W is thussubjected to low-temperature tempering, and the hard and brittlestructure formed in the second heating process S15 and the secondcooling process S16 is transformed into a tempered structure havingimproved toughness, for example.

Next, as shown in FIG. 10 and FIG. 23 (d), the jig 100 as shown in FIG.8 (a) is then lowered again by the transfer loader unit 220, theworkpiece W on the jig 100 is disposed in the cooling section 500, andwhile the workpiece W is rotated, a large amount of cooling liquid isinjected to the workpiece W from the cooling jackets 520 installed at aplurality of positions to cool the entire workpiece W.

The tempered workpiece W is then suspended with the jig 100 by thetransfer loader unit 220, transferred to the bring in/out section 300 asshown in FIG. 3, and the heat treatment of the entire areas to beheat-treated H1, H2 of the workpiece W is thus completed.

According to the heat treatment method as described above, sincering-shaped areas to be heated H1, H2 corresponding to the shape of theworkpiece W are provided at a plurality of positions of the ring-shapedworkpiece W, and the plurality of areas to be heat-treated H1, H2 aresubjected to heat treatment sequentially, heating can be performed bythe heating unit 450 corresponding only to the shape of the areas to beheat-treated H1, H2, regardless of the size and shape of the workpieceW. As a result, the heating unit 450 can be made to be in a simplestructure independent of the size of the workpiece W or the shape of theworkpiece W itself. In addition, unlike the case where all the areas tobe heat-treated H1, H2 of the workpiece W are heated simultaneously, thepower required for heating at the same time is smaller, and thus thepower feeding equipment can be made to be in a simple structure.

Furthermore, according to this heat treatment method, when thering-shaped areas to be heat-treated H1, H2 provided locally at aplurality of positions of the ring-shaped workpiece W along the shape ofthe workpiece are sequentially subjected to heat treatment, heattreatment of the first area to be heat-treated H1 is performed in thefirst heating process S11 and the first cooling process S12, thetempering of the first area to be heat-treated H1 is performed byheating and cooling the first area to be heat-treated H1 in the firsttempering process S13, and then the second area to be heat-treated H2 isheated. Consequently, occurrence of heat treatment defects such asdeformation and hardening cracks can be decreased or prevented duringthe time until the second area to be heat-treated H2 is heated, orduring heating.

In this case, the workpiece W where the deformation amount on one edgeof the second area to be heat-treated H2 caused by the heating of thesecond area to be heat-treated H2 differs from that on the other isused. With such a workpiece W, since the workpiece W deformsnon-uniformly when the area to be heat-treated H2 is heated, heattreatment defects such as deformation and hardening cracks tend to occurin the first area to be heat-treated H1. In this embodiment, however, byperforming tempering, heat treatment defects can be preventedeffectively.

The heat treatment method in this embodiment performs induction heatingusing the same heating coils 451 in the first heating process S11 andthe first tempering process S13. It is therefore unnecessary to provideheating coils 451 separately, and so the structure of the heat treatmentequipment 10 can be simplified.

In addition, in the first heating process S11 and the second heatingprocess S15, the first area to be heat-treated H1 and the second area tobe heat-treated H2 are induction-heated by using the same heating coils451. It is therefore unnecessary to provide heating coils 451separately, and so the structure of the heat treatment equipment 10 canbe simplified.

Furthermore, the first area to be heat-treated H1 and the second area tobe heat-treated H2 are in plane-symmetrical shape, and after the firsttempering process S13, induction heating is performed with the workpieceW inversed. It is therefore possible to share the heating coils 451, andin addition, the positional adjustment of heating coils 451, etc. canalso be simplified, and the heat treatment of workpieces W having aplurality of areas to be heat-treated H1, H2 can be facilitated.

The above embodiment can be modified as required within the scope of thepresent invention. The example where a workpiece W having two areas tobe heated, namely the first area to be heat-treated H1 and the secondarea to be heat-treated H2, was subjected to heat treatment wasexplained. However, any number of areas to be heated can be adopted,provided that it is two or more. When ring-shaped areas to be heated areprovided at three or more positions, by following tempering processevery time quenching of each area to be heated is completed duringsequential heating of the areas to be heated, occurrence of heattreatment defects such as hardening cracks and deformation can besuppressed when the next area to be heated is subjected to heattreatment.

The case where the first area to be heated H1 and the second area to beheated H2 are in plane-symmetrical shape was explained above. Even ifthe inclination, width, etc. of the second area to be heated H2 differfrom those of the first area to be heated H1 when the workpiece W isinverted, by adjusting the disposition and orientation of the pluralityof heating coils 451, the second heating process S15 can be followedusing the same heating coils 451.

In addition, if the shape of the first area to be heated H1 and that ofthe second area to be heated H2 are completely different, it is possibleto apply the present invention as well by performing heating byreplacing the heating coils 451 for the first heating process S11 andfor the second heating process S15.

The example where the workpiece W was in the shape of a ring wasexplained above. However, the workpiece W may also be in a form of aplate, rod, bulk, etc., on condition that a plurality of areas to beheated H1, H2 can be provided in a shape of a ring.

In the above description, the temperature was increased to 170□C to200□C and cooling was performed in the atmosphere of the air in thefirst tempering process S13 and the second tempering process S17, but itis also possible to adopt other methods.

LIST OF SYMBOLS

-   W: Workpiece-   W1: Base-   W2: Protrusion-   W3: Inclined surface-   H1, H2: Areas to be heated-   C: Rotation center-   P1: Bring in/out position-   P2: Suspending position-   P3: Heating position-   10: Heat treatment equipment (heating device)-   12, 12A, 12B, 12C: Transformer-   13, 13A, 13B, 13C: Matching unit-   14: Inverter-   14A: Rectifier unit-   14B: Inverter unit-   15: Inverter control unit-   15A: Rectification control unit-   15B: Inversion control unit-   16: Group of switches-   16A, 16B, 16C, 16D, 16E: Switches-   17: Switching control unit-   18: Setting unit-   19: Commercial power supply-   40: Heating/cooling rack-   42: Displacement rack-   43: Position detection column-   44: Position detection rack-   100: Jig-   110: Workpiece supporting member-   111: Radial rack-   112: Rotating roller (relative transfer means)-   130: Central structure-   200: Transfer mechanism-   210: Transfer rail-   220: Transfer loader unit-   246: Rotation driving means-   255: Rotation driving motor-   300: Bring in/out section-   400: Heating section-   410: Jig supporting mechanism-   440: Auxiliary cooling unit-   450: Heating unit-   451: Heating coil-   452: Supporting box-   460: Displacing means-   461: Position adjusting handle-   462: Vertical displacing unit-   463: Horizontal displacing unit-   464: Lower rack-   465: Vertical driving mechanism-   466: Displacement guide rod-   467: Vertical displacement screw shaft-   468: Displacement bearing-   469: Vertical driving motor-   471: Connecting body-   472: First displacement rail-   473: Upper rack-   474: First displacement driving mechanism-   475: Second displacement rail-   476: Second displacement driving mechanism-   477: Displacement driving motor-   478: Horizontal displacement screw shaft-   479: Displacement protrusion-   480: Position detecting means-   481: First expanding/contracting mechanism-   482: Second expanding/contracting mechanism-   483: Radial position detector-   484: Axial position detector-   485: Driving means for expansion/contraction-   486: Rod-   487: Guide rod-   488: Contactor-   489: Variation detector-   490: Posture control unit-   491: Power adjusting means-   492: Angle changing unit-   493: Setting input unit-   494: Arithmetic processing unit-   495: Storage unit-   496: Heating state evaluating unit-   497: Driving control unit-   500: Cooling section-   520: Cooling jacket-   600: Parts replacement section-   700: Power feeding equipment-   701: Mobile terminal-   702: Cable-   710: Operating unit-   711: Input/output screen

What is claimed is:
 1. An induction heating equipment, comprising: a plurality of induction heating devices disposed at intervals along the circumference of a ring-shaped workpiece; a setting unit for setting induction heating conditions; and a switching control unit, wherein each of the plurality of induction heating devices comprises: heating coils disposed facing areas to be heated of the workpiece; a plurality of transformers connected to the heating coils in parallel; a plurality of matching units connected to any one of the plurality of transformers; an inverter unit having a rectifier unit for converting commercial power voltage to DC voltage and an inverter unit for converting the DC voltage obtained by the rectifier unit to a voltage having a specified frequency; an inverter control unit having a rectification control unit for controlling the rectifier unit and a plurality of inversion control units for controlling the inverter unit, thereby obtaining voltages having specified frequencies; and a group of switches for connecting the heating coils to any one of the plurality of transformers, connecting any one of the plurality of transformers to any one of the plurality of matching units, connecting any one of the plurality of matching units to the inverter, and connecting any one of the plurality of inversion control units to the inverter unit, wherein the setting unit sets frequency setting information on the voltage output from the inverter and the selection information of matching circuits, namely combinations of selections of the plurality of matching units and the plurality of transformers, for each of the induction heating devices, or for each of the divisions obtained by dividing induction heating time into a plurality of divisions, as induction heating conditions, and the switching control unit selects any one of the plurality of inversion control units, and controls the inverter unit, thereby outputting a voltage having a specified frequency, connects a matching unit to the inverter, connects the matching unit to a transformer, and connects the transformer to the heating coils by using the group of switches, for each of the induction heating devices and by the division, in accordance with the induction heating conditions set by the setting unit.
 2. An induction heating method, comprising the step of: varying the frequency of induction current to be fed to the workpiece depending on the heating temperature or heating time of the workpiece when a workpiece is induction-heated while being moved; and changing the combinations of matching units and transformers in accordance with the change in frequency.
 3. An induction heating method, comprising the step of: disposing a plurality of heating coils along a workpiece; varying the frequency of the induction current fed to the workpiece depending on the heating temperature or heating time of the workpiece when induction heating is performed by the plurality of heating coils while the workpiece is moved; and changing combinations of matching units and transformers depending on the change in frequency.
 4. A heat treatment method for providing a plurality of ring-shaped areas to be heated along a ring-shaped workpiece and performing heat treatment sequentially for each of the areas to be heated, comprising: a first heating process for heating a first area to be heated; a first cooling process for rapidly cooling the heated first area to be heated; a tempering process for heating and cooling the first area to be heated after the first cooling process is completed; and a second heating process for heating the second area to be heated after the tempering process is completed.
 5. The heat treatment method as set forth in claim 4, wherein the deformation amount that appears on one edge of the areas to be heated when the areas to be heated are heated is different from that on the other.
 6. The heat treatment method as set forth in claim 4, wherein the first area to be heated is induction-heated by using the same heating coils in the first heating process and the tempering process.
 7. The heat treatment method as set forth in claim 4, wherein the first area to be heated and the second area to be heated are induction-heated by using the same heating coils in the first heating process and the second heating process.
 8. The heat treatment method as set forth in claim 7, wherein the first area to be heated and the second area to be heated are in a plane-symmetrical shape, and the workpiece is inverted after the tempering process. 